Wonder if its just my GC, I have had nothing but terrible experiences there. Glad you found what you wanted though!
Tough to get more than 60% of average retail price for a trade in from GC or any other music store. If you have something extremely rare in great condition they may be willing to give a little more but overall anyone can get more selling locally or through Reverb, EBay, etc.
I’ve only done one trade with a retail store ever and that was because of the price they had my Strat listed for and their willingness to offer me more for my Tele than I paid for it. I may have gotten $50-$75 more for my Tele had I sold it locally but I would have missed out on a like new $950 Strat for $600.
When it comes to selling or swapping gear I’ve had more success with Music-Go-Round.