Well oh my goodness this is a topic with so many sides, and while I will normally defer to manX I do have a different take on:

"Unless buying second hand from a trusted source, any of those mentioned are so inexpensive, why would one?"

For me, it's more than just a transaction. I really enjoy haunting the music swaps. Thanks to my son I have become somewhat of a regular on Saturday mornings... just browsing, talking over coffee. Most know me by name now. I get to mess with stuff, buy something if the price is right and I am interested, and at the same time I know because the original purchaser took the initial "bite" on devaluation, I will probably come out ok if I want to part with something.

So many angles to this. Have fun!