Actually, you're not suppose to sell names to the trademark holder (if any) for amounts in excess of your out of pocket costs.
You are not supposed to have registered a name for the sole purpose of resale. But we know a bunch of people did. I did not.
I have never sold a biz, but have bought several. This one was acquired from a registrar that owned it directly.
WIPO has held up that you can change your mind on development and sell for the highest amount you can get. Or, you can develop it and offer it for sale as well.
Well, I'm going to sell this one, but want an appraisal first.