I think it depends on how cheap.
Lets say the seller listed them for $7 instead of $70. That's more than likely a mistake.
But if they listed them for $58 instead of $70. They seller could of been looking to just make a sale and get their money back.
Stubhub does have the fan protection, but you would be more than likely to get a refund than replacement tickets if this is too good to be true.