Just stumbled across this.
Batman is $12.49 USD from Games for Windows, as can be seen here:
http://www.microsoft.com/games/en-US/games/pages/sales.aspx
DoWII is £5.00 as seen here:
http://uk-thq-eshop.gamesplanet.com/pc-games/buy-download-Da…
I think you can add DoWII to Steam, but don't quote me on it.
That link says Batman is US$12.49.