DDR2 RAM prices have been going up strongly over the past month at wholesale (I was looking at one Corsair module today -- the wholesale cost went from $107 to $172 in just six weeks).
You can expect to see prices varying, even daily, as companies jockey for price with the manufacturers, and competitively aginst each other.
Be suspicious of much lower than average prices, those will be companies who haven't updated their advertised pricing and your order will be rejected or you'll get the 'we have a small problem' phonecall when you try to get the 'deal'. To be safe, verify your price on the phone or by email the day you plan to order.
Thanks
Trevor
CanadaRAM.com