The "Federally-facilitated Exchanges IT" contract awarded to CGI Federal Inc, which is the one that includes building the Healthcare.gov website among other services, was $55 million. The numbers are directly from the Government Accountability Office's report:
http://www.gao.gov/assets/660/655291.pdf
That's still a big number, but it's over an order of magnitude less than yours. It should also be noted that not all of this money is coming from taxpayers. The GAO estimates that in fiscal year 2014, $450 million in fees will be collected from the insurance companies participating in the exchanges, and this money is directly credited to the account used to manage the FFE program.