I have a couple of sizable sofas and I really like them. The back cushions are feather and are now collapsed and saggy. I priced up feather covered foam and it is about £170 a cushion. Problem is I have 9 cushions! Foam only is about £75, but I don't think that is the right look.
So we are getting into the realms of whether it makes more sense to get new sofas. Mine are about 8 years old, but basically fine and comfy. But they weren't crazy expensive. The cost of new cushions is the cost of at least one sofa!