If you look at the price of sd ram, its still expensive too. sd ram and rd ram is still in demand, so manufacturers still produce it for the minority. ddr ram will be cheaper because its one, being produced at a greater rate, thus lowering production costs. But also because the market is so competitive. Everyone is trying to outdo their rivals so prices slowly go down. In this case market competition has lowered prices so much that it costs less to buy ddr than sd ram.
But it's wierd because I can buy Corsair XMS DDR400 PC3200 1GB Dual-Channel for $260...while a Samsung 512MB PC800 RDRAM is $207.
RDRAM wasn't all that cheap to begin with among other things, and didn't help it's popularity. For those that needed the higher performance RDRAM offered before dual-channel DDR came along, particularly with the i840 and i850 chipsets, you didn't really have an option. RDRAM was on it's way out after Intel put out Granite Bay, or the E7xxx chipset. The main problem with RDRAM was that it was proprietary, and anyone wishing to produce modules needed a liscense, and part of their profits on RDRAM went to Rambus. The other issue that didn't help anything is the high latency it had. Rambus the company didn't do itself any favors when it falsely claimed patent rights to certain parts of JEDEC standards on SDRAM and consequently DDR. This was part of the reason that Intel dropped RDRAM from their chipset roadmap. IMO, if Rambust hadn't gone ahead and started suing companies on their claim of patent rights on SDRAM technology, they might have had a brighter future.
