Nice topic. Well, I am using a 3rd hand K2/10W right now. My only rig. I won't list the QRP tcvrs I have bought and sold. All have been used coming in and, naturally, going out. Except for the K2, they have been inexpensive, built from kits. Bought cheap and sold cheaper...or given away. I will very likely be picking up a couple of modestly priced HW-8 Green Machines. Will be nice to have them again without breaking the bank.
I think the cost of a current ICOM, Elecraft, etc. high-tech modern transceiver a bit too high to permit casual collecting. But, there are great, inexpensive QRP fun-kits out there so that you can scratch that QRP rig purchase itch when it arrives.