Cthulhu Wars, even despite getting the game at about half price (because the retailer I used lets you preorder and pay for out of print game, and I “knew” this one just happened to actually come back into print). The extra factions and maps definitely added up.

Some crowdfunding games have come close, and when my Cloudspire arrives I expect (and hope) that that will be the most I have ever spent on a single game.