They can be had quite cheaply when they come up, which isn't often. I have a minty example for alto with a 6 facing, which I picked up on UK Ebay for £10.00. It is a really good player, so I recently bought a 5 with a nick in one rail for $25.00, thinking I might eventually send it to Morgan Fry. I paid more serious money for a tenor 5 which had been opened to an 8 by Hervé MARTIN (reputable French refacer). 8 is about as open as I can play on such a large-chambered low-baffle mouthpiece, but it still responds very well.
I think they're well worth searching out, and I'd be interested to hear other people's experiences with them