The seller's dilemma is that its on the seller to accurately describe the lot. Or to say that they simply don't know.
But when a $5 marble is described as a $150-175 marble - then the sellers reputation suffers. Thats just how markets work.
I understand the conflict that you mentioned, but again.... if you have 2 or 3 conflicting IDs, you have the choice whether to list it - or wait for a better ID. Choosing to list it described as the highest value of the 3 possibilities..... makes people wonder.
Selling at shows simplifies the process a lot. Folks that have been in the hobby a long time have seen a lot. Not all of it good. There will always be heightened awareness of misidentified marbles being sold - especially when the error is significantly in the seller's financial favor.