The laser scanner is kind of fancy, but you can get USB scanners for $10-$20 that present as keyboards. For me, the most interesting part of this is looking at Elixir.
An important thing for secondhand ones is to download the manual; it will contain a set of configuration barcodes so you can factory reset it, turn off beeping, etc.
The only differentiation I can see is the really expensive ones can scan the tiny 2d codes that are silkscreened on some ICs, and the cheap ones are limited to about the same resolution that a standard consumer printer can print a barcode at. Unless you have some very specialized requirements, you should be good with just about any cheap barcode scanner.