GL 7 is a volatile book and prices have been all over the map. I agree, Ebay has a wider audience, and books can be sold more quickly. There are quite a bit of GL fans right now to support the prices. GL 7 will no doubt do well when the GL movie releases, but for the long term, SC22 is a better book.
I agree that SC #22 is the better book, but GL #7 can be had for much cheaper due to lack of widespread awareness and represents a better flipping opportunity than SC #22 right now. The lack of awareness on SC #22 ended last August/September.