All the time! They will even tell me why they need to pay less than the listed price!
Of course, I am basically making bespoke product, so that's different.
I have best offer turned off, but they still send messages trying to get things for less than I have listed them. My pat answer is that I am making these on demand and typically sell through the quantities I list, so it's not something that I am looking to unload.
And then, when I have a slow weekend, I very often send offers of $5-$10 off to people watching the listing.
All of that said, pretty much anytime I buy something at a vintage toy store or a toy show, I will always offer them like $10 less since I am paying in cash. It usually goes pretty well.