Valve and Steam are the same company so when they gave free Steam keys to PS3 purchasers there was no cost liability, Valve aren't going to waive their publishers fee just because Bethesda wants to fix its PR. (not that it wants to, but I imagine that's your reasoning for this request)
The trouble with the games industry is that it feels entitled to the best of both worlds. It defends itself against things like warranty and guarantee by saying that they're selling not a physical product but a license to piece of software but neatly sidesteps the fact that licenses should be interchangeable across platforms by saying that the software disc is a physical product - catch 22 for consumers.
I got stung by Fallout 3 and once I progressed so far my game was unplayable, so I borrowed the PC copy from a friend and used that to see all of the content that Bethesda's lack of due dilligence prevented me from accessing on the PS3 (and this was before the DLC even released). I had absolutely no qualms about keeping that game on my PC and playing it after giving my friend his disc back because as far I'm concerned I had a license to play the game and Bethesda failed to provide me the means to play the game the way I chose to. My advice, borrow the game from someone else and play it the way it should have been released because Bethesda surely won't fix our version and certainly won't offer any sort of trade scheme.