Your using RIMMs *cringes*
DDR ram is not as expensive as your RDRAM, just because people are actually supplying it, but there are a lot of variables in how much the ram will cost.
G5 is PowerPC based, or technically its Power based, and PowerPC is Power based, but oh well, same difference. Will this core be similar to G5? Yes, probablly so, except it probably won't have the altivac. I doubt they are just adding up the cores to 3.5ghz, and I doubt that is the actual number, probably just what they are wanting to get to. Honestly though, if they were just 1.16ghz, that would be a very slow computer, in fact, 3 cores at that speed would be just about useless. 3.5ghz, is their goal, though I doubt they will achieve it.
Ram type, My bet is on DDR2-800, possibly some XDR (yellowstone, ya the same thing on PS3) form. They may go with GDDR3 1600, but thats still up in the air, but I am doubting they will.
FSB on these processors I would expect to be 1ghz, with a total theoretical bandwith of 8gb/s. DDR-2 in dual channel can pump 12.8gb/s (again theoretical).
GDDR3 can pump 25.6gb/s in dual channel, 51.2gb/s in 256bit arrays. That is up to what is promised by XDR, and is currently planned on being used in this generation of video cards. However, this is going to be expensive, and a 256bit setup will require atleast a 6layer PCB, so this is going to make for an expensive motherboard if this is what they choose.
There are a lot of options available to the makers, but I would expect this system to rival a high end system today, just because of the what is known of the gpu, and when it arrives a mid range system.