The guitar is an Epiphone Masterbuilt DR500MCE. Dealer says will take 80$ off the price. Fair? How big a deal is this? Guitar sounds wonderful otherwise
That sort of thing happens when the guitar is squeezed too hard while in a gig bag. To fix it properly, your luthier needs to employ a tool called a brace jack, which is a mini version of what you might use to jack up a sagging joist under your house. There is loads of gluing surface, plus it's the back and not the top - prognosis is good.
I would probably charge around $40 for that repair in my shop assuming no other issues, for reference.
I don't see it as a big deal. I ain't no luthier butwas able to repair broken braces in a 1920s Regal myself using one of those brace jacks mentioned in an above post.