@Springfairy556 Sorry I wasn't totally clear on what you were asking before. But yes, you can transfer your saves and other content from an Origin install to a Steam one. The only exception is store stuff, which would have to be reinstalled (but could of course be redownloaded for free). I did this a few months ago, also moving from mac OS to Windows, and everything went fine.
Steam usually has a sale around New Year's, and last year, the prices were exactly the same as you're seeing now. That's no guarantee, but there have been a few similar sales so far this year, so it's entirely feasible to rebuy the game. Just remember that the packs you own in Origin would not transfer to Steam—you'd have to rebuy them all.
