I'm not sure price is an issue. Although I haven't seen any DDR3 as yet, normally when a new one comes out it isn't interchangeable with any of its predecessors. Unless they've now changed that, price makes no difference. Also, as soon as a new one comes out, the price of the old goes up.
Charming people these manufacturers - aren't they?
Check online for pricing. You should probably compare form the same manufacturer and performance level.
Saga, what do you mean you have not seen any DDR3 yet? Been in use for a year if not more.
Obviously my customers don't have very up to date machines. Most of my work these days doesn't even involve opening the case - malware fixes, mostly and I would only physically see the latest type of stick if I had to take one out and replace it. Also, with my ageing eyesight and having worn specs for sixty years, I still find it hard to spot the difference between DDR and DDR2 and to tell which is which at a glance, I have to refer to a known stick of DDR. Try looking quickly and see if you can tell one from the other. A 184 pin stick with the gap in a slightly different position is, to my mind, hard to identify.
My original point stands, therefore - why would anyone need to compare prices? The price comparison which might be valid would be in the motherboard which can take either type of stick. If Bystander is building a new box, surely he or she would want to have the latest to future proof the system.
Fastest way I use to tell DDR from DDR2 or 3, is that DDR is made from larger chips and uses side connections. DDR2 has smaller chips and uses a ball grid array connector wich the connections behind the chips, so the chips look to "float" on the board. This won't work well for DDR2 vs DDR3, but will let you tell DDR vs. DDR2 at a glance.