Eh I was quoted $75 for my tops, cut them myself from 3/8" off Craigslist for $20. Only checked with one glass place though, might have been a high quote?
Sure, in that scenario, it makes sense. Most of the time finding glass and meeting someone on craigslist, buying a glass cutter and sanding down the edges usually is more running around then ordering good 1/4" glass over the phone and picking it up already polished. Not to mention if someone doesn't have any experience doing it and screws up their glass. I've been cutting my own glass for aquarium tops and window replacements professionally for a long time and guarantee I have scars from doing it older that most members here. I honestly think it's as cheap, or in some cases cheaper to have it done by a honest glass supplier.