$10 depending on quests done.
Decent stats pure stats that I would pay for:
60 att (with LC and MM done)
85+ str
1 def
85+ range
15-52 pray
94 mage (with DT done)
80+ hp
80+ dung
Rest of the stats wouldn't matter to me as long as they were high enough to complete quests such as DT, MM, RFD, etc. Common pure quests.
I would personally pay around $50 for an account like ^, that would be 100-120mish.
Edit: Botting is so prevalent now that account prices have gone down a lot, plus supply vastly outnumbers the demand. If you want an account to go up in price a lot, train skills that are harder to bot or cost a lot of money (prayer, herb) or quest the shit out of the account.
But just a generic pure such as the one I made up, wouldn't be worth the money you can get if you do it be hand.