I used to negotiate contracts for a living and what you suggest is not negotiating. When someone offers .50 and you come back with 2.00 you’ve established your ceiling. If you go back the next day and say it’s not 2 but 3, that’s negotiating in bad faith. I’ve had that happen to me and it almost led to the collapse of the contract. Now, there’s nothing that says you can’t do that because until a contract is signed, theoretically you can ask for everything. However, don’t expect it to go over well.