I've had the sorts of deceptive VAT-excluded offers Michael describes. They're certainly irritating.
I've never accepted one, mind you, because I have a policy of either making offers proactively or counter-offering in response to offers speculatively made by sellers.
The snag with the second of these is that once a seller has sent you an offer speculatively, eBay's software then prevents you from making a counter-offer in response; you have to either accept or decline the seller's initial offer. The make-an-offer feature, if it was initially present, will have been removed, and every time you log back in and return to the item the seller made you an offer on you still have to either accept or decline that original offer.
Meanwhile, if you log in using a different account and go to the item, the make-an-offer feature will still be there large as life should you choose to use it.
A recent transaction illustrates the case. A seller sent me a speculative offer on some NOS Dormer drills. It was a risible 1% off the BIN price. I wanted to make a counter-offer, but couldn't. I messaged the seller directly and proposed a more generous [to me] discount. He refused even to negotiate and repeated his offer of 1% off the asking price. Needless to say I didn't respond.
Three days later I logged in using a different eBay account. The item was still listed with the make-an-offer feature enabled. I made an even lower offer than my original higher offer that the seller had refused, and the seller immediately accepted.
I do find that some sellers on eBay don't understand the psychology of bargaining, and the people who write eBay's software seem not to understand much about anything at all.