About 100$/hour for skilled professional I would assume. Big companies that need extra help for a short time period I would guess 200$/hr.
Anything below 50$/hr would be a good deal if he/she can deliver the goods.
I assume you're thinking of the US? You can probably find some guy in Asia that does the same thing for 10% of that, with more than a couple of potential issues though. (Not skill-wise, but communication/culture-wise particularly.)
That said, until the OP specifically states what platform he needs his game to run on and how much initiative is required by the programmer, it's kind of impossible to give an accurate answer. If you can give a programmer small verifiable atomic tasks it will require much less on the programmer's behalf than a large complex task, particularly if it is to be carried out independently.