What do you mean by prefab counter tops?

A prefab countertop is simply a finished section of counter, in a "standard" size or configuration. If you have sections of counter where you can use that, then that's great. All that needs to be done is to install it. No fabricator services needed.

https://www.msistone.com/prefabricated-countertops/quartz/

More often, you may still need an edge trimmed or a sink cut out done, so a fabricator will need to do that. So it does not matter whether the material is a full slab, or a "prefab" size - if you need the material to be cut, you will need the services of a fabricator.

One Houzzer named beth often speaks of prefab granite and possibly quartz which do need to be cut to size by a fabricator. She is from California. These counters are supposed to be much less expensive - but you do have to pay a fabricator to cut them. I have not seen this available in my area - but then I haven't been looking either:)

Laminate also come in stock sizes that are very reasonable. Some come with the pre-mitered corner. I used this for my basement kitchenette. The stock length of one piece was too long and my installer cut it to size and added the laminate end caps.

Often countertops are ordered through a K and B store and are delivered and installed by specialized installers. GCs work with these installers - sub this job out and do not do it themselves. It takes specialized tools to cut, polish and seam stone and quartz counters, and many GCs do not have the tools.

jhmarie - read what I posted above. Yes - if you need something CUT, then you need a fabricator.

I used one in our dorm apt in Maine. It was good old Formica and it fit perfectly in the space. Of course, it sat on top of 3 mis-matched white cabinets, two of which I got for next to nothing. The third came from our basement at home - it had been taken out when we did a bit of work in the kitchen when we bought the house. I painted it white, and cut a hole in the door and used it for a cat box. We didn't even attach the countertop to the cabinets - gravity held it nicely in place. It gave me a nice 8 ft run of counter space in a kitchen that had 3 ft. And the price was just right for a faculty dorm apt. When we left, the development office at the school, wrote us a letter that we had donated it to the school, and we took the value as a tax deduction.

In my area most of the lower grade granites now come prefab, even though you work through a fabricator and they never mention the fact. You still need sink and range cutouts, etc.

In CA it did use to be a great deal, sometimes. I can remember a woman over at ikeafans back in the day who got Chinese marble countertops for a medium-sized kitchen for about $600, including a team of Chinese craftsmen who did the installation. I doubt there's anything like that now, though.