I just looked at your for sale posts and saw your latest reply above and I think I see the issue. You’re trying to trade. This complicates values, limits your audience, and limits your selection.
Think of your guns as a form of currency. They’re not USD, but what you want to buy from PSA is in USD, so they have to be converted. If you do the conversion by selling them privately, great, it’s now easy to go buy what you want. However, if you want a gun shop to convert your currency, you’re now asking them for a currency exchange service AND a gun, so you’re going to pay for that. Using a common currency (USD) is far more efficient 98% of the time than trying to trade or barter.
I have no clue what your STI is worth but if you sell it here for 20% off fair market value, you’ll still be far ahead of the ~50% a gun shop is going to offer. Then you can take that cash and buy whatever you want wherever you want.
My $.02