My understanding was that most LFS made there money through their maintenance accounts... At least that's what I've read in all the postings about wanting to start a lfs.
No doubt that is one avenue most are exploiting, but there are no guarantees there either. Sales are much harder to come by but good if you can get them… Just like everything else I guess. Takes extra capital, extra insurance, and you have to be away from the shop to do it. So it implies employees as well. No magic bullets, just more hard work.