It depends on how technical you are.
I have a $1200 Chinese knockoff one and it works fine. The software is a pain to use, but I do all of my design in inkscape and just use their software to cut/engrave. I do have to tune it up once a month or so, but that only takes an hour or so. The intial setup/tuning took a couple days, but it was not hard.
You can spend $15k+ for a nice Epilog or Universal, and they do have a lot of really nice features. With a good quality commercial one, you can print directly from your image software, not have to fiddle with it, and get higher power/smaller kerf. If you are looking to engrave names and such on pens or engrave acrylic, the cheaper one will be fine as long as you maintain it. If you want to make laser inlay kits, then you will probably want to get the commercial units. There are other differences, but those are the simple ones.
PM if you want more info.
If I could afford it, I would either buy an Epilog or build one from scratch. There is not a significant difference between a laser cutter and a gantry mill. Either can be built for about 3k with a 4'x4' cutting area.