tardtasticx: I totally dont understand why you're forced/sued to go through with it.
He hasn't paid you a cent (you havnt mentioned him sending you money?)
Neither of you signed anything, only exchanged various details and agreed on a price via sms.
And like someone said above, if he has to get a loan to buy a licence plate, why would be have enough money to go and get a damn lawyer to "sue" you.
IANAL, but I believe an SMS , and even verbal contract can be considered a binding contract.
Not everyone has 10's of thousands in their account. It may have been an investment, or they may have purchased for someone else, and they would then make a margin. They also may have lawyer friends who will do it probono. You can't really assume anything.