I like the COLLECTOR aspect of retro gaming as well as playing the games. I LIKE having ALL my SMS, Genesis, 32X, Sega CD, Saturn, Dreamcast, PS1, PSP and PS2 and the vast majority of my Game Gear Games complete with packaging, instructions and whatever extras some games happen to have like posters and stickers. I have all the boxes and instructions for all my peripherals and systems too, call me nuts but I like this stuff. I bought many of my retro games new back in the day so it was really pretty easy to compile the bulk of my collection and I've always kept my games in nice shape and complete.
For those few games I missed from when they were new, I don't mind hunting them down and paying a little extra for a complete copy vs. a loose copy. The thrill of the hunt is part of the fun. I'm not rich but my bills are few and money isn't really a show stopper if I really want something which is why in the past few months I've been able to add a Nomad, CDX and the games Snatcher and Popful Mail to my collection. Believe me, even at my level of collecting this hobby is much less expensive than my other hobby!
That said, I don't simply throw silly money away to get that gem, I'm a cheapskate at heart but I really do shop for the best price for the best items available. But at some point you have to pay more than a few bucks to get certain items. Haggling too is a lost art and it's fun. Sometimes you can get a rare gem for a bargain by doing someone else a favor or by being a loyal customer and being a friend. If you remain on the hunt often enough, sometimes bargains walk up and jump in your lap.
The other point of view is, I don't understand how people can stand to own loose carts or discs!

It makes them feel so, incomplete. I have probably well over 250 games across all my systems so having all complete games is no small accomplishment and I'm proud of the fact that my games and system are complete with all the stuff most people threw away when these things were new. I guess my game room is as much an interactive museum as it is a play room.