I always think of even minor mods, that for every $1 I have invested (perhaps with the exception of a Borla or Corsa exhaust), is exactly $1 lost. But if the money I spend on that mod brings years of happiness as I own it, that is what is important to me.
As to major mods, such as hopping up a motor, I think you sadly experienced that many feel about such major mods as a liability, fearful of how the previous owned treated those steriodical upgrades.
Sorry you took a bath today. But now you can recover, and plan ahead as to what will be your replacement Corvette. It might work out well for you buying as late as you can, for next spring and beyond, those of us who are trading in our pristine C7’s (getting an ME) are going to take a bath, e.g., expecting about 50 cents on the dollar for my impeccably maintained, 20,000 mile, 2015 Z06. And so when that happens, some C6 owners are going to be selling theirs, smartly looking for a great condition C7 trade-ins or private sales, and then some C5 owners will trade up, etc.
Best of luck finding what you are looking for.