A house is never finished. It needs repairs, it needs to be remodeled as time goes on, it needs replacements for old appliances. To continue the analogy, cosmetic DLC released at launch is like the gardener being permantently attached to the reconstruction of a dilapidated building. You pay the gardener to put in some trees and bushes, and it's relatively cheap. Since remaking the garden from scratch is relatively easy compared to refitting the building with new pipes and wiring, the gardener finishes very quickly, while the building is still being refurbished. The gardener did everything that was asked by you, but has nothing to do for the next 8 months or so. So the construction manager approaches you and says that, for an additional sum of money, he can keep working, putting in flowers and various statues. That is to say, there was a certain amount of work that was designed to be put into the game. That includes just a handful of models, no unique ones. If you want more than what was designed to be in the game, you can have it, you just have to pay for it.