Oh, I was referring to the tip (gratuity), not the price of the
service. You'd have to pay for the indicated cost of the service,
but could always vary the amount of the gratuity depending on your
perception of the quality of the service received.
Haircuts here in the US typically cost anywhere between US$7 and
US$12, depending on whether or not a coupon is used; I normally add
a gratuity of US$2 to that amount, but have on occasion withheld it
if I felt the barber didn't cut my hair the way I requested her
to.
I used to have my hair cut by an Indian barber down the road from
my house in Singapore, and would customarily throw in an additional
S$2 tip to the price of the service as I felt he did an excellent
job. My dad and I had been going to him for haircuts for over 10
years before he retired and went back to India.