If two persons want to trade then its normal that both dont have the same terms in mind. If the seller suggests to sell you something and you say yes, by sending the money, then its the problem of the buyer since he agreed to what the seller wanted to sell.

I think buyer had to confirm first if he gets what he wants. The seller only wrote what he can offer.

Only my opinion... maybe other users think differently.  

Edit: Oh and how did he scam you for $10? Did you await to get the account for free? If you awaited $5 loaded then it would be $5 scammed, if at all.