Of course GC and others are idiots. But you guys are the fools. You all need to learn how to "shop like a woman".
First you don't want the instruments tuned or fixed or in anyway repaired PROVIDED that you can do the repairs. You don't want them cleaned or knobs tightened or anything else that is minor. Can you do a setup? Can you adjust a truss rod? Can you tune a bass? Can you clean the crap off the bass? Can you tighten jacks, switches and controls so they aren't all loose and rotating all over the place. If you can't then go buy a new bass from some high end store, pay the cash and go play it.
But those of us without money to burn, CAN do those fixes. And each one detracts from the asking price of the instrument. Hey, even if I have to rip ALL the controls out of a bass, yeah that's a serious repair but certainly within the realm of my abilities. So just HOW do you guys suppose I got my Ken Smith burner 6 string? By forking over a few grand? Come on. It was $300. It was high mileage and even the tuners had to be replaced. The only real expense beyond parts was a fret job by the local luthier ($80).
Hosed management is not a "problem" it's opportunity knocking. When a store is full of idiots (as was the local Sam Ash store for years until they started to clean up their act) you see all manner of weird things. You simply laugh at and ignore all the things priced higher than new prices and scarf up all the things priced nearly free because the clueless store manager has no idea what it is. I can't tell you the vast amounts of money I've saved due to clueless store management. I've got music gear like a king and paid next to nothing for most of it.
Of course if YOU are clueless and don't know how to tune your bass or replace a knob then you are just an opportunity for someone else. There was a local bass player who'd buy all manner of new gear, play it for a while, get unhappy with it and then sell it used for a song. That guy supplied me with SO much stuff for next to nothing I was really disappointed when he finally found a rig he liked and quit buying new stuff.
On the other hand you ALSO have to know your limitations. A twisted neck is probably not going to be fixed by you (except by a new neck if that's possible). The fret job on my Ken Smith was scary until the luthier managed to fix it. (replacing all the frets is much more expensive than just leveling them).
But in spite of all this, never forget that when you see a bargain, BUY IT. "ya snooze, ya loose" is the rule. The bottom line is that if *I* am out there looking for things I can fix and pick up for a song, there are some other people out there who ALSO can fix them. There are quite a few footprints all over my butt from cases where I thought I'd think about something until tomorrow. Bzzzt. Too late.
And as for having work done at a GC or similar store, forget it. Our GC is pretty good, but It's pretty obvious that the "repair department" is that they asked among the clerks to find who knows how to change strings or do a rough setup. Search out a real luthier who knows what he's doing. It will be a much bigger bargain in the long run.