What the cost-of-living calculators miss
Most tools flatten the Austin versus Seattle comparison into a single percentage. That number hides almost everything that actually matters.
Both cities are in zero-income-tax states, so the Austin-to-Seattle comparison is unusually clean on tax math. Washington does have a 7% capital gains tax on gains above $270,000 that Texas does not have. For ordinary wage earners, the states are equivalent.
The house is where Seattle gets expensive. Median Seattle home price runs $852,000, versus $548,000 in Austin. That is a $304,000 sticker delta, which at current rates works out to about $1,700 a month in mortgage payment on the same down payment.
Rent tracks the same direction: $2,650 median 2-bedroom in Seattle, $1,895 in Austin. A Seattle renter pays roughly $9,000 a year more than an Austin renter for the same two-bedroom apartment.
Seattle clawbacks: lower homeowners insurance ($1,188 vs $4,456), lower auto insurance ($1,464 vs $2,228), and lower property tax effective (0.76% vs 1.80%, which on the bigger Seattle home still comes out close in absolute dollars).
The Seattle sales tax is the highest of any US metro at 10.35% combined. Every taxable dollar you spend pays about 2.1 cents more than the Austin equivalent. For a family spending $35,000 a year on taxable goods, that is $735 per year.