Turned up, inspected item, gave the seller the money (had offered more than they originally were asking for - popular item). Handed over what i thought was the right amount of money. The seller helped unpack the item so says they didnt count the money which is possible
They were apparently the housekeeper, selling the item for owner of the house.
Now after get home getting messages that i didnt pay the full amount and that their boss will be "super angry" and they will have to pay out of their pocket. I was already paying $100 more than what was originally asked for by the housekeeper/seller.
Asked them to sign a statutory declaration that they only received $300 and I will transfer the $50 they say i owe. They've now said it's too much effort.
Have i done the right thing?
They've decided signing a piece of paper isn't worth $50 to them, end of matter. (No, you haven't done the wrong thing).