Well, almost. People may not want infinite things, but they want more things that other people have.
Or even better, things that other people don't have. As outward sign of their higher status. It is not about needing something, it is about showing up your neighbours. Post-scarcity is impossible, because artificial scarcity will be immediately invented. Another commenter mentioned that artificial diamonds don't differ from mined ones anymore, but everybody still wants the natural ones. That's good example of artificial scarcity used to create status symbols. So let's say we can 3D print cars, houses, whatever. This will simply make 'real' (not-printed) items more valuable.