Like others have said, these home shop guys probably don’t have all the overhead that larger shops have. thus why some are probably willing to do the jobs for less.
Overhead for sure, they also don’t have a warranty which to me you would have to save a lot of money to trust a vehicle repair that might lead to an accident to some dude in his garage. I understand the guy you were talking about did not work at a shop but regardless cutting a hole to save time is shady at best.