Accounts is just a really tricky thing. I personally would not be up for this as there can be workarounds or people just get on Skype and sell for lower than their thread and there's nothing to stop this.
I tried something a while back to prevent account scams, somewhat. But I haven't really been active to update it and it's just gone to garbage lately, unfortunately.
I think the best way is just to try and educate people. Setting a minimum price isn't going to help too much, in my opinion. People are going to scam regardless and setting a minimum will just now let scammers get more money for the accounts they're planning to recover anyway. It's not really helping aside from delaying the sale a little bit due to the increase in price.
Edit: And honestly, unless you're getting the account to just stake, stats and XP isn't a true indication of an accounts worth. There are a lot of extra stuff that adds value to an account besides just XP.