If you can order a lot at once, Munro's is a great place to shop. They carry the Fimo clays and the QuickMix http://www.munrocrafts.com/Fimo-Polymer-Clay-s/4002.htm
If you buy $200 worth of stuff, you get a 50% discount, which is pretty darn good. :) Their online ordering discounts are as follows:
FOR SHIP OUT ORDERS:
Minimum order of $25.00 for ship out orders.
Orders under $50.00 - no discount on retail prices
Orders $50.00 to $100.00 discount is 25% off retail prices
Order over $100.00 discount is 40% off retail prices
Order over $200.00 discount is 50% off retail prices.
Items that are cost, with no discount, are final sale. Items include but are not limited to: Books, Magazines, Austrian (Swarovski) Crystal Items, Czech Crystal, Kraft Paper Bags & boxes, Sale Items, Charms, Bali Silver, Beads/Pearls sold by the strand, cut or counted items, Mystic Maid products are priced wholesale, no further discount is applied.