If you find yourself visiting NYC from time to time, I suggest you visit CanalDev in China Town (it's across the street from the slightly-more-legit Canal Hi-Fi). I've found ten-packs of Sony Gold Prisms for fourteen dollars and no tax; quality-wise, they're just below the Sony porcelain-white ES series. I've also bought most kinds of pro and designer MD blanks there (Axia, Sony Sparkle, Music Jack 2000, Neige, XS-ive, Denon, HHB, etc.) and paid far less than than I would have on the web. The comparatively cheap price was the only reason I bothered to experiment.
BTW: How's Carnaby Street these days? I found lots of good music stores there while I was recording at Cajun Studios in the early nineties.