I’ve only had people offer rarely, mainly on Apple products. But where I think it might happen I usually add a very clear note now in the description, saying please don’t make an offer, I won’t accept it. And that seems to work almost all the time. I added it to my current auction, where I thought it might be an issue. But it’s not really a factor in most Big Finish CD sales :)

Eg this is what I have on my current auction:

Please note: I will not end the auction early, or accept offers to do so. Please don’t ask. Thanks.