Yes, same here – most items I’ve put up I haven’t really known how much I wanted to get for it (I was just having a clear-out and it needed to go) but I’ve always said on the auction listing I wouldn’t consider any offers because it’s fairer for everyone to let the auction run its course. Let the market decide its value.
Yet each time I’ve had plenty of messages like yiman lists above, the chancers who will ask “how much for buy it now?” or will say “I’ll give you £XX to end the auction early”.
And literally every single time I’ve politely declined and let the auction run to its finish, and every single time it’s finished for a higher value than any of the offers I’d received. If it’s attracted the attention of chancers, most times it’s attracted the attention of genuine bidders, and even those who have made offers but are serious about the item have waited til the end of the auction to bid properly.