No disrespect but I do think you’re wrong.
Bad buyers target sellers of all levels, although in my experience they are most likely to hit on new sellers without a level.
Over the years I have learnt that buyers who try to drive the cost down from the start or ask for more services than a gig offers are not worth dealing with. They’ve set out their pitch from the beginning - they’re going to be trouble. Forget them.
Why are you providing unlimited revisions? That is crazy. You are almost inviting bad sellers to order from you and then abuse you. They will be attracted by the ‘greed’ element, but you will never please this type of buyer - as you have discovered to your cost.
I’m not saying my way is right, but I don’t offer any revisions. I still get sales. If I’m feeling generous and the buyer seems a decent sort, then I will be happy to help them out with a revision if they later ask, but I don’t make it part of the gig.
Your premise that as your seller level goes up, the buyers get worse is wrong. It’s all about how you sell your gig and yourself, and how you manage buyers.