Legal Question in Product Liability in California

I would imagine your Dad would be fine giving you an extra $300 after you got him an additional $2700. If your father refuses, I would suggest that it isn't worth family strife over $300.

The answer to your either/or question is neither one exactly. You have a verbal contact that is missing a provision that was not anticipated and agreed on. If this was a big case, say you were a broker and you were authorized to list a house for $700,000 and you managed to sell it for 1,000,000 a court would most likely rule that what you are entitled to is 10% on $1,000,000. You generally only get a profit if you buy something and sell it for a higher price because you put your money at risk. So if you had bought the set for $6,300 expecting to sell it for $7,000 and got $10,000 the extra would be yours. But when you are merely a commissioned seller you get your commission on the sale, period, unless you negotiate beforehand to get a bonus on any sale above the seller's asking price.