So far, the best price in SF for 2 hours of pure bliss -- $35-$50 facials. Waxing is super cheap too.
One thing to be aware of is that you are not in your own private room, but rather with three other clients. It doesn't make one bit of difference after the first 5 minutes. Sort of like a nail salon for facials. You can always schedule an appointment with a friend.
Located on 20th @ Irving.