Legally, no--if they quoted you a price then did the work before teling you there might be a different or additional charge, they are limited to the price they had quoted and you had agreed to pay. They may not charge you more than you agreed to pay after they have done the work. (If they had shown up and told you that there would be an extra $25 for the additional floor *before* they did the work, you could have either agreed to pay or told them "no thanks--I don't want the work done." What they can't do is after the fact increase the cost without your consent.)