here's the GS pay schedule, for reference: http://www.opm.gov/oca/12tables/html/gs.asp
note how you're not going to crack 6 figures until the end of your GS-14. How long does it take to get to GS-14? somewhere between 5-10 years in service, if you're lucky. if you're not lucky, you might never make it.
why so long? because advancement through grades is entirely based on time in service. there is nothing your management chain, up to the president, can do to pay you more. it would take, literally, an act of congress.
hooray! oh yeah, as a graduate with a CS degree from a good (CMU, MIT, etc) school, you will start as a GS-7 or a GS-9. which is about 40k. 2nd tier tech companies and consulting companies will start you at literally double that. if you are really good, companies like msft and amazon will start you at literally TRIPLE that.
so... how is this a choice for anyone? why does the government delude itself that it isn't about the money?