It's not preposterous within a certain income range. If your household income is $300,000 in SF (for a married couple), your net pay is about $14,800 per month. If it's $150,000 in Kansas City, MO, your net pay is about $8,600 per month. So you're talking about an $6,200 per month difference.
You can buy a 3BR, 2,000 square foot in Overland Park, a great school district, for $200-250k. You'll be about a 15-20 minute drive from your work downtown. What does a 3BR, 1,700-2,000 square foot house run you within 15-20 minutes of downtown Mountain View, in a good school district? It looks like $1.5 million+. That's the difference between a $7,200 per month mortgage and a $1,200 per month mortgage.[1]
So housing alone almost completely wipes out your extra income. Then you have other costs that scale with cost of living: house cleaning, after-school child care, etc. You'll pay more for gas, you'll pay almost double for a cocktail, etc.
Obviously, once you're up to $1 million per year, your're better off in San Francisco. But even in SF few programmers are earning that much. $300k is a solid household income in that area, and in that range you're not better off, materially, than you would be in Kansas City.
[1] A family making $300k in the Bay Area is getting close to not even being able to qualify for a mortgage big enough to buy a house close to work.