Depends what you're getting... you can always sell your standard buildings (houses, culturals, and supply buildings), and decos can be turned into goodies in the recurring quests, but that's unfortunately not going to work on event and premium buildings. On the plus side, you can still use them for quests of the "build bla di bla of your age".
But in general I'm with you on this... once you got a dozen of any building sitting in your inventory, winning another one's nearly as thrilling as ToR BPs. Why oh why did the brain boxes at Inno decide to cram even more buildings into the rewards at the expense of goods and FPs?