Why do you put it that way? Everyone serving in military takes home a paycheck, but that doesn't make them mercinaries.
The top tech talent that we aim to attract to USDS often can make far more than these salaries staying in the private sector, so appealing to a sense of civic duty and offering short-term engagements is what we have to do to recruit.
Of course, if you're a student, they have no problem pulling you out of the classes that you might be paying several hundred a day to attend, without comp...
Market for the people USDS is hiring generally is higher than that in cash, plus better benefits, plus 50-100k/yr in equity. There is some sacrifice, but not an insurmountable one.
Honestly, that's much better than I was expecting. Two years working to improve our shitty government systems in exchange for a quarter of a million? Sounds like a fair short-term deal, even if higher comp is available elsewhere...
The actually-doing-tech-work GS levels (GS-10 to GS-13), by comparison, are 50-60k. That is where government pay is still the big impediment.
$116k/yr for your entire mid/late career would also suck (compared to 200-400k in industry), but for <2 years, I can't see that alone being a huge issue, unless you have kids in college, are paying for a mortgage elsewhere, etc.
(From va.gov/ds/, where I work, I believe this is the same for all the other Digital Service teams though)