I'm guessing three things could happen:
The masseur is not looking to do anything beyond an erotic massage, so he declined,
He accepted but for a new rate/price, or
He accepted while not changing the rate (because he was just horny as well).
To those who've experienced it, how did you and the masseur agree on the new rate (if option two happened to you)? If options 1 or 3 happened to you, feel free to share your story too!