I also want to use Gates GT 3 belts. I requested a quote from CMT (
http://www.cmtco.com/) and they replied in less than 24 hours. The price for the stock pulley (P/N 24-3MR15-6FA.250) was $12.95 @ for 12 pulleys and delivery was 4-6 weeks. Guess everything is made to order.
Will give them a go.