The 800XL was a major price reduction from the original 800. In addition to manufacturing and component cost improvements, FCC regulations relaxed a bunch between the original revision and when the 800/600XL came out. So they were able to drop a boatload of RF shielding, just like the VIC-20 and C64 could. The inside of the original 800 looks like a bloody Faraday Cage.

And by that point in the 80s the original 1979 Atari 800 case design was starting to look really 70s. At least that's how it seemed to me as a kid. The 1200XL/800XL case looked so slick. It's up there with the Sinclair QL and some of the Japanese MSX machines in terms of case design, IMHO.