A lot of things, yeah. The problem is broadly that their manufacturing is already so expensive that it doesn't make sense to sell it without all the other parts. Like my moonroof blew out and it needed the glass, and the rails replaced. Hypothetically I could get a used part to replace those five things (four rails one glass). But no such used part existed. Instead I had to purchase the entire roof assembly and replace the entire roof. It turns out that moonroof glass is a loss leader for SUV makers.