Not cheap, but you won't find decent S775 quad cores cheaply nowadays... I bought my Q9550 just in time, it went out of stock the next day at eBuyer, and I haven't seen it in stock at a reasonable price anywhere else since! I paid about £175 for it I think.
DDR2 is also far too expensive, I think Amazon had some Kingston for £65 for 4GB which was cheaaap at the time - it's £60 now.