Having moved from the Maryland suburbs of DC, to the outskirts of Indianapolis, back to Maryland, and planning to move back to Indiana, these are the two areas I know about, and I can say that there are a lot more reasons besides money to move out there. Lower population density, for one, leads to much, much less traffic, which is positively heaven sent. The air is cleaner. The crime is lower. The east coast - where much of our most dense areas are - have horrible, muggy summers. I could go on.
But as we are talking about money, let's look at this link comparing the cost of living between the two cities.
Indy costs 89.8 of the national average; move to DC, and that becomes 142.8. Looking at housing alone, that stretches out to 74.4 vs. a staggering 235.2. Think of that as meaning that the $74,400 single-family home in Indianapolis will put you back $235,200 in DC. In simplest terms, your mortgage payment will more than triple. It takes a lot of higher-paying job to make up for that, and the average per capita income difference of $23,800 vs. $43,500 isn't enough to make up for that. The short answer: Yes, jobs in DC pay more, but not that much more, and that's why people like me are moving out.
Incidentally, Kansas City, Missouri, is 94.2% of the national average overall, with housing at only 70%, so you guys can get houses for less than even the Hoosiers can. Income per capita is $24,900.