> This one is too expensive for me...so I'm out, sorry guys...
in postcard exchage you have to send a card to every participant of that round, or you select a slightly smaller amount of cards. So you have to deal with 20-40 cards every round.
In BPX you have to send only one, but usually larger print.
Costs are not that expansive, if you avoid sendig a real huge print overseas. A decent print can be sent in a large enveloppe.