I really doubt you are going to get a deal done by offering under market price.
Actually the market price is really what a buyer and seller are willing to do a deal now for.
The exchanges market price usually takes into consideration lots of factors, what it last sold for, buy order,s sell orders, and volume, given the inactivity of the position the stated value is not reliable. Notwithstanding, isn't there other changes one must go through to convert GLD to fiat when dealing with an exchange? Doesn't it have to be converted to a "major coin" then cashed out? What happens when GLD is down and the "major coin" is up, you loose value there. Is there any liquidity value -- there's no wait time for my funds.
I don't think any of that are real factors, I think everyone is waiting for the value to go higher, in the mean time inactivity is causing the value to go down.
I offered over exchange value price and I've offered under, yet the response is the same -- no deal.
I give up.