The money is not small at all. If he succedes in getting that amount from you, here's going to try it with more people and that will eventually add up to something that's very big. A reputable vendor before setting his as should already have the amount that's to be used for the payment, if for any reason the amount isn't available or went short for whatever reason, the most honourable thing to do is to council the transaction and save himself from all the drama.

I just hope that any vendor that tries to be unnecessarily smart while doing P2P is reported and given negative trust so People can avoid such vendor because if allowed, they will continue to fill the space and overtime make it hard to identify which vendor is a scammer and which is not.