There's a lot of factors to this including how much the spa charges, massage quality, special ending..etc. So, in the scenario of a regular run of the mill spa like Greenhouse spa or Spa 27 which charges $60 per hour, and a regular massage (not spectacular, but good enough which is common), and an engaging manual HE, What is your regular tip? (knowing that performances that go below or above would dictate adjusting it.)
$60?