We are brought in either under Intermittent Consultants or Schedule A hires. This means that in exchange for being able to hire you by name rather than going through a more structured process through USAjobs.gov, you can only work for 2 years. Therefore, no matter what the pay, it's probably not a viable long term career.
It's also important to note that this is probably a good thing - I've been at Healthcare.gov and USDS since Jan of 2014 and I'm finding that I'm getting adjusted to some of the bureaucracy. It's therefore actually key to balance experience with fresh perspectives.
I'd also say that the salary ranges - it's in part based on what you used to make in the private sector but has a hard ceiling. For everyone who comes, it's more than enough to survive but not a long term career move for anyone. And of course, there are no stock options or equity stakes :D.