People collect different things for all different reasons. There are many people that make geocoins for their signature items.
I considered doing a geocoin in August of last year. I did the design, worked through a couple of iterations of the icon and quoted the whole thing out to the tune of US$1399.00 for 250. WOW! and I was ready to do it, too.
Then I found out about a new thing called PATHTAGS. They are about the size of a quarter, the cost was US$99 for the die and first 25 tags, and then $99 for the next 100. I thought it was a great deal for what was going to be a personal item anyway.
I have 8 designs now and have traded for over 150 of the existing designs as well. I don't think I would have been able to afford that if I were doing geocoins.
BTW - Pathtags ARE trackable to an extent, not on GC but through Pathtags.com. You can see who has logged your tag and where they logged them at (coordinates). It's still early but I can see this really taking off. We Love em!
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