Hello Wayne and the Group,
I too am an avid "paper" QSL collector. Last year, 2007, I sent nearly 2000 QSLs out. It's much too soon to calculate the return results for last year but after 47+ years I'd say that 50% would be a great return.
Recently I contacted a fellow in Hungary since I still need satellite confirmation from that entity. I have worked three HAs but many dollars and many attempts direct and via the bureau have netted me zero return.