They needed more memory and a faster processor as well which bumped the price up. In the mid eighties I worked for a company distributing QMS printers in the UK. A basic laser was selling for £2,000 and the PostScript equivalent was £4,000.

Printers of the 80s and early 90s were more performant PCs than the typical PC which printed on it. Because you can't process full color 600 DPI page on the 90s PC with 8-16 MB of RAM, but the printer needs to do that.