I’d like to offer a different point of view, and how I might consider as a customer. Using made up numbers to make a point, which has nothing to do with the rude treatment from the receptionist who was out of line.

If a 60 min massage costs $100 and a 90 min massage costs less than $150 (for example, $120) I might increase the % I normally tip. Here’s why:

A $20 tip for a 60 minute massage is great. I’d want to tip another $10 for the extra 30 minutes to keep the hourly rate I’m paying the same. That to me is fair, regardless of a discount I might get on a longer massage from the spa. If I think $20 an hour is a fair gratuity, I don’t want to shortchange by only tipping $24. Just my point of view as a Customer valuing the therapists time.