So, out of curiosity, and let's take everyone involved out of this, and make it a landscaping business. If I have workers that work on a commission base, and they agree to take $100 each for a job, and the base price for that job is $1,000 then why should I then, after they've agreed to $100 each give them more when the owner agrees to pay double because it's cold outside? The workers agree to a price, and they get payed that price. If I take more from the person paying for the service I don't owe those workers anything in a legal sense. In a moral sense maybe, but that's not the concern here.
So let's apply that to this situation. In the picture he provided he priced it at 9m, that's the price he agreed to, and the price he agreed to being payed. That's the price he was payed. Whatever else happened in the transaction is none of his concern.