I think it's likely that there is a higher concentration of tech (esp. software engineering) jobs in some of the further flung suburbs than in DC proper, which yields some more affordable options (sometimes at the cost of some urban amenities).

This is not a lot cheaper than what you quoted, but for ~$2k/mo you can rent a 1 BR apartment in one of those relatively new, relatively fancy condominium-style medium-rise buildings at Reston Town Center (essentially the "downtown" area, or at least one of them) which puts you in very short walking distance of a bunch of tech offices and even a good number of nightlife and entertainment options. You could easily live the "15-minute city" life there. It would be a little bit like living in a large outdoor mall, but it's a very walkable "neighborhood". (EDIT: the DC metro system is also within walking distance.)

There are a handful of other "tech hubs" like that scattered around the DMV.