No, that's a very expensive server, and Dell will charge you a hefty premium for the memory. There are quite a few options that will cost you less than that (of course the maximum capacity will vary).
It would be nice to see an article comparing all the high RAM machines side by side with specs and prices.
The largest machine I have right now will hold 512G and was a run-of-the-mill machine, it was about $5K, I'd expect the more exotic ones to be substantially more expensive but probably not as expensive as the machines linked here.
I can get Octal rank in bulk for ~$1K so that's $16 or thereabouts / G, still not bad for RAM that is obviously going to be sold in smaller quantities. Note that HP or Dell will probably not be happy if you use 3rd party RAM in their machines (if they didn't pull tricks to make sure only their own stuff works!).
(For contrast, that $1K if you'd spend it on HP branded RAM would not even get you four 16G dual rank units...).
