Try Steam, they still sell it. http://store.steampowered.com/app/900883/
Thanks for the link, Ni! <--how do you pronounce your screenname?(j/k; I have the movie. hehe)
I did see that Steam sells the GOTY, which is good. It still doesn't answer why Bethesda or D2D no longer sell it, however. Why only one place to DL the game? It just seems kinda strange, considering you can get Morrowind at a few places, but not Oblivion.
This feels strangely similar to the price jump for Planescape: Torment. For a while there, it was selling for over $60.00 for a +10yo game! Oblivion came out 5 years ago, so the $90.00 for the Disc seems pretty jacked up to me. Mebbe it's because I already bought the GOTY edition before, but having a lame computer, I wasn't even able to finish, and now that I can run it full-bore, I'm really looking forward to seeing just how beautiful it is, before Skyrim makes me not want to bother.