I've been in to collecting for a half the time you were (though solving for far longer) and I'd say wow. I have exactly half the number of puzzles you do. You must have spent tons of money on this stuff, since that's the limiting factor for me. I buy things once I get the money. Is that you too?
A friend and I figured out that i could sell my collection for around 700$ but i've spent no where near that. A few of the puzzles were given to me and others are rare ones that i bought for a cheap price and could sell for much more.
When it comes to buying puzzles, if I find a puzzle i want i'll usually buy it if its a reasonable price and its not something i already have. Its been a while since ive bought one though.
It's fully printed in White Strong and Flexible (kind of like me! )