According to the Taschen website info (which for some reason my computer will not let me link to) the new "nice price" edition is slightly smaller and doesn't include a slipcase.
Limited edition: Hardcover, slipcase, 27 x 34 cm (10.6 x 13.4 in.), 378 pages
"Nice price" edition: Hardcover, 24.9 x 31.4 cm (9.8 x 12.4 in.), 376 pages
It doesn't mention any other differences, but I would assume that the limited edition is more of a traditional art book, with high quality paper and printing processes.
I would guess that the smaller, cheaper book quality will reflect the fact that it's being mass produced.
Just my guess....
Chris