I think the annoyance is that they weren't interested in giving tours until someone asked, and they figured out they could make a profit. Pretty reasonable to expect a ticket, even if it isn't free.
If I were the factory owner, I would reserve a ticket for him and give a discounted price to thank for his idea.
Maybe having somebody reach out for a tour was just red flaggy enough. I agree it’s weird and kind of crummy to then offer an auction up.