Years ago, wasn't there a proposal from google or the likes to have push notifications for search engines? Instead of the bots checking offer and offer again if there is something new, you would inform them about it. I think that would be a fair middle ground. You don't ddos us and in exchange we inform you timely if there is something new. (Bot would need a way to subscript themselves.)

I have a personal website that sometimes doesn't get an update for a year. Still the bots are in the majority of visitors. (Not so much that I would need counter measures but still.) Most bot visits could be avoided with such a scheme.