It's not a job you go into for the money. They're making like twice the median income for the US, that's more than enough to live comfortably. Frankly, you don't get involved in that line of work without some serious patriotism.
If you're single 105k in DC is amazing. If you have a family, you will have everything you NEED, but you won't be living by most peoples' definitions of "very comfortably".
A lot of those positions aren't in high cost areas, especially if you don't have kids. The area near Fort Meade, MD isn't too bad. San Antonio, TX is reasonable. Aurora, CO (just outside of Denver) isn't bad either, neither is Augusta, Georgia. A starting salary of $70-$80k for a recent college grad goes a long ways in those areas.
Fort Meade, Maryland? Are you kidding me, I'm in the DC area you're looking at close to a 1/2 million dollars for a reasonable house in a decent neighborhood in that area, not to mention Maryland's taxes are some of the highest in the country. On top of all of that, you have neighboring PG County, Maryland where corruption and crime are out of control, as well as terrible traffic around the entire DC metro area. Of all places you mentioned, Fort Meade does not belong in the same lot.
Living in coastal California, I wish I could buy a reasonable house in a decent neighborhood for close to 1/2 million dollars. In the neighborhood where i'm currently renting it's strictly 800k+, and I'm in one of the least desired elementary-school districts in town.
Where are you looking? There are some bad areas for sure, but there are certainly good areas with decent pricing (Talking about ~30min drive to NSA or defense contractor in the area, if you are speaking about closer then disregard).
Living near Fort Meade is the most expensive of that group, but it's still a lot, lot less than DC or SV.
I've priced stuff out in that area. It's not as bad as you're making it out to be. There's a number of decent areas with reasonable housing, it only gets more expensive if you're concerned about also having a shorter drive into DC.