I'm fine with dlc as long as the game is complete without them, that is:
- the game is of average length or more
- no essential quest/items requires dlc's
- you're not constantly spammed in game by quests you can't complete without dlc
As long as these criteria are fulfilled I'm ok. I don't think it's especially greedy, and I don't think it makes much sense claiming that it's charging for content that should have been in the game for a larger than average game. You could say the same about addons.
Regarding the cost of dlcs versus the value, it's up to the customer to decide whether it's worth it or not. Admittedly they tend to be a bit costly. In Oblivion I bought most dlcs, but not the horse armour. In most cases I were happy with the purchase.
Come to think of it, addons aren't exactly cheap either. At around half the price of the original game and extending gameplay by 20%, it is a bit steep, I think.