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Why a cheaper COL index can still leave you worse off

A cost-of-living index will tell you a city is 18% cheaper. That is not 18% more leftover. Sometimes the 'cheaper' city keeps less money after tax and rent, because the index never met your paycheck.

By Mason Hahn · Last updated · hello@uprootmap.com

The sentence an index cannot finish

The companion piece, leftover is not a cost-of-living index, is the design argument: indexes price a basket, skip income tax, and treat every household as average. This page is the arithmetic. Six pairs. Same leftover engine as every city page. Two households — the site's default local nurse, and a $120k remote salary held flat — so you can see when “cheaper on COL” and “more leftover” agree, and when they do not.

A published COL score is usually something like “Boise is 8% below the US average, Seattle is 40% above.” The implied move is obvious. The leftover move is not, once local pay for the same job falls harder than rent. That is the failure mode this page exists to show.

Seattle vs Boise: cheaper on paper, less leftover on a local paycheck

Washington has no state income tax. Idaho does. A COL table still paints Boise as the bargain of the inland Northwest: smaller, cheaper housing, cheaper restaurants. On the default local nurse paycheck, leftover goes the other way. Seattle's wage for the same occupation is high enough that take-home stays ahead of the one-bedroom, and Idaho's tax plus a softer local wage leave Boise behind.

  • Leftover in Seattle: $3,409 a month after tax and rent (take-home $7,298, rent $1,758).
  • Leftover in Boise: $2,001 a month (take-home $5,314, rent $1,383).
  • Gap: −$1,408 leftover a month if you make that move on this household — move page, line-by-line compare.

Flip the same pair to a $120k remote salary and the story calms down. Pay no longer falls when you leave Seattle, so Boise's cheaper rent finally shows up as leftover — a small gap, not the transformation a COL percentage advertised. If you are local, the index picked the wrong city. If you are remote, it picked the right direction and the wrong magnitude.

Same pair, paycheck held at $120k remote, one adult, one bedroom:

  • Leftover in Seattle: $3,842 a month after tax and rent (take-home $7,731, rent $1,758).
  • Leftover in Boise: $3,918 a month (take-home $7,231, rent $1,383).
  • Gap: +$76 leftover a month if you make that move on this household — move page, line-by-line compare.

Chicago vs Austin: the tax the index never invoices

Illinois charges a flat wage tax. Texas charges none. A COL index comparing grocery and rent baskets will say Austin is a bit cheaper than Chicago, or about even, depending on which vintage you grabbed. Leftover on the default household is not “a bit.” It is a tax line you stop paying plus a one-bedroom that costs less than Chicago's, which is why the Chicago → Austin move page is a leftover page and not a slogan.

  • Leftover in Chicago: $2,426 a month after tax and rent (take-home $6,079, rent $1,782).
  • Leftover in Austin: $3,181 a month (take-home $6,418, rent $1,221).
  • Gap: +$755 leftover a month if you make that move on this household — move page, line-by-line compare.

Austin's property tax will matter if you buy. It does not appear in a renter leftover the way a wage tax does. That is honest, and it is also why leftover is a filter: the Austin housing topic is where the buy- instead figure lives. An index that blended owners and renters already hid that fork.

New York vs Miami: both 'expensive,' different leftover

COL commentary treats New York and Miami as two flavors of expensive. They are, if the question is restaurant prices. Leftover is a different question. New York City adds a local income tax on top of New York State. Florida has no wage tax. Miami rent is high; New York one-bedroom asking rent is in another league. On the default nurse paycheck the destination keeps more leftover. On a remote $120k the gap widens, because you stop paying the city wage tax and you do not lose a New York wage — you never had a local one.

  • Leftover in New York: $1,249 a month after tax and rent (take-home $6,412, rent $3,018).
  • Leftover in Miami: $1,690 a month (take-home $5,972, rent $2,073).
  • Gap: +$441 leftover a month if you make that move on this household — move page, line-by-line compare.

Remote $120k, same bedrooms:

  • Leftover in New York: $1,668 a month after tax and rent (take-home $6,831, rent $3,018).
  • Leftover in Miami: $3,449 a month (take-home $7,731, rent $2,073).
  • Gap: +$1,781 leftover a month if you make that move on this household — move page, line-by-line compare.

If your COL spreadsheet said “both are 20%+ above the US, so it does not matter,” leftover disagrees by hundreds of dollars a month. That is rent plus a tax the index did not model. The state tax and rent guide is the longer version of city wage taxes.

Philadelphia vs Pittsburgh: a local tax, not a vibe

Same state income tax. Different city. Philadelphia's wage tax is the plot on this pair — leftover barely moves on the default local paycheck because Pittsburgh pay is softer and the rent gap is not huge. Remote $120k, pay held flat, and the city wage tax is finally visible as leftover: Pittsburgh keeps more because the 3.75% line item is gone and rent is lower.

  • Leftover in Philadelphia: $2,437 a month after tax and rent (take-home $5,864, rent $1,530).
  • Leftover in Pittsburgh: $2,526 a month (take-home $5,520, rent $1,163).
  • Gap: +$89 leftover a month if you make that move on this household — move page, line-by-line compare.

Remote $120k, where the wage tax is not offset by a local raise:

  • Leftover in Philadelphia: $3,622 a month after tax and rent (take-home $7,049, rent $1,530).
  • Leftover in Pittsburgh: $4,130 a month (take-home $7,124, rent $1,163).
  • Gap: +$508 leftover a month if you make that move on this household — move page, line-by-line compare.

A COL index that stops at the state line will rank these two cities by groceries and a blended rent. It will not tell you the tax you file with the city. That is why the Philadelphia vs Pittsburgh compare exists as leftover, not as “western Pennsylvania is cheaper.”

Boston vs Raleigh, and San Francisco vs Houston

New England COL tables love to say the South is cheaper. Sometimes leftover agrees. Boston's one-bedroom and Massachusetts tax against Raleigh's rent and North Carolina schedule leave a real monthly gap on the default household, and a larger one when pay is remote. The index got the direction right. It cannot tell you whether the gap funds a move — that is how much leftover you need.

  • Leftover in Boston: $1,967 a month after tax and rent (take-home $6,643, rent $2,549).
  • Leftover in Raleigh: $2,736 a month (take-home $5,948, rent $1,252).
  • Gap: +$769 leftover a month if you make that move on this household — move page, line-by-line compare.

California wage tax plus Bay Area rent versus Texas and a Houston one-bedroom. A COL index will scream “San Francisco is 70% more expensive.” Leftover on a local nurse paycheck is a few hundred a month, not 70% of a nurse's life, because Houston pay is also lower. Hold pay at $120k remote and the leftover gap becomes the thing people meant by that 70% — thousands a month — because the expensive city no longer pays you more for staying.

  • Leftover in San Francisco: $2,364 a month after tax and rent (take-home $7,413, rent $2,635).
  • Leftover in Houston: $3,161 a month (take-home $6,299, rent $1,188).
  • Gap: +$797 leftover a month if you make that move on this household — move page, line-by-line compare.

That last sentence is the whole site: an index assumes an income. Leftover asks you which income. The San Francisco → Austin leftover corridor is the sibling of Houston, written out as a move people search. Do not average them. You will live in one city.

How to use these examples without turning them into a new index

Do not build a spreadsheet of “COL % versus leftover $” for 387 metros. That is how leftover turns back into a ranking toy. Use the pairs as a test for a move you are already considering:

  1. Write the COL sentence you keep repeating (“Boise is cheaper,” “Texas is cheaper,” “the South is 20% less”).
  2. Open the two city pages, or the compare, on the household you would actually run — local occupation or remote salary, bedrooms you would sign.
  3. Read leftover, then the tax line, then the rent line. If leftover disagrees with the COL sentence, the tax or the wage or the unit is why. The mistakes guide names the usual shortcuts.

Then go look at listings. Leftover is a filter. A COL percentage is a conversation starter that should not survive first contact with a paycheck.

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