One thing I'll mention is that we always seem to get Spa coupons delivered to the cabin 3 or 4 days into a cruise, for something like $80 off anything.
Using a coupon, as a male, I get a free haircut, as they are priced from $49- $79. (Yes, I still tip)
My wife uses one to get a whole hair package for about half price, which makes is comparable to services at a salon at home.
And we both love the service and quality of the cut and care.