These are some of the top sites. Pricing for a P99c in .40 should be anywhere from $525 to $620. They have quite a big price difference depending on who you get them from. I know at my local range they sell them for about $580 plus tax, etc.
I'd highly recommend you check your local dealers first. See if they can order one for you, and maybe you can haggle down the price (most places don't have them in stock.)
The best prices I have seen for most Walthers (if in stock) is www.budsgunshop.com. $523 plus shipping($25) and transfer.
Those prices at WaltherClearingHouse pretty much blow, btw.
Not a flame just an observation. Surprisingly, a local shop has the P99Cs priced at $549 which I consider w/in the normal price range.
So for me it would actually be cheaper to buy the P99C locally vs. ordering from Buds.