What the numbers mean
A $75,000 salary in Los Angeles gives you the equivalent of $40,318 in purchasing power after accounting for state income taxes (7.0%) and the local cost of living. The same salary in Austin gives you $61,983 — a difference of +54%.
Median rent in Austin runs about $1,700/month — roughly $700/month less than Los Angeles's $2,400. That's $8,400/year back in your pocket before you factor in anything else.
No state income tax in Austin. On a $75,000 salary, that's roughly $5,250/year you keep that you wouldn't in Los Angeles.
These numbers use a cost-of-living index where 100 = national average. Los Angeles's index of 173 means it costs 173% of the national average to maintain the same lifestyle. Austin's is 121.