I don't sell Pyrex here, but I am a major Pyrex lover and collector! It does seem that the older and more rare the piece, the more it is sought after. The patterns from the 70s, like butterfly gold, spring blossom, woodland, etc. are plentiful. Any trip I take to Goodwill I can usually find a couple of these pieces. On the other hand, though, Friendship is from the 70s and is extremely popular- and hard to come by. I don't know for sure....it just seems that the bright pops of color from the 40s and 50s and the kitschy pink and turquoise of the 60s are the most sought after right now. But don't give up- somewhere out there is a buyer for groovy 70s Pyrex!