As it stands now, most sold accounts are used for non-scamming purposes
Do you state this from your first hand involvement in Account trading?
What are "non scamming" purposes? Presumably they involve a financial benefit, so are you referring to signature campaign income?
if the sale of accounts were disallowed then the buyers who buy accounts for non-scamming purposes would no longer wish to buy accounts
Which would mean that "the non-scamming purpose" market would shrink, or need to be opened up to newbies.
but the number of accounts for sale would remain the same.
No it wouldn't, it would mean that account farming would be much less attractive because of the danger of all the accounts belonging to the farmer being rendered worthless.
Basic economics would imply that the price would go down, reducing the costs to potential scammers
No, because above: supply would drastically reduce.
Unless you're talking about the $10 loan market, does the cost of an account really figure in the number of scams pulled? Imo, no, IYO, probably yes.
Tl,dr:
Pros
More difficult for scammers
Less sig spam
Account farming made unprofitable
Cons
None.
But nothing will change.