Now, assuming he bought Oblivion at launch at $60, then bought all the DLC at full-price, you're looking at a price of roughly $116 (actually a little less, but I rounded up for the DLC prices to make calculations easier). Divide that by 1000 hours played, and the OP spent roughly 12 cents for every hour spent playing Oblivion.
Personally, I think 12 cents an hour to play Oblivion with all the official plug-ins (except maybe Horse Armor, but Bethesda definitely learned not to do stuff like that anymore) is totally worth the money, but thats just me.