How much government money have the Birthers spent?

They were tying up a lot of staff time at the Hawaii Department of Health, until HI passed a law basically allowing staff to tell people to buzz off if they became a nuisance record requester.

A couple of secretaries of state in various states have had to siphon off some attorney general staff time to defend a variety of nuisance suits brought against them as "ballot challenges".

In a couple of federal suits, a handful of DoJ attorneys have appeared.

Not a whole lot, unless you count the opportunity cost of court time.