Bitt, what I usually do is buy my CDs in batches on eBay. I will look for something I'm really interested at the time and then will scan through everything else each of the sellers is offering. This way I can buy multiple discs from one person and save on shipping. The last time I did it, I think I averaged less than $5 per disc after shipping. That included a couple of rare discs I was willing to pay a premium for, which obviously increased the average.
This past weekend I purchased 6 discs from one person in one auction, but it was something I was willing to pay a premium for - and take the time to snipe manually. All 6 CD releases from The Ocean Blue which came out to about $50 with shipping (the seller is even in the province and the discs are probably at my mail box come to think of it.)