We pay $80/hour, twice a week at a library near our home. Worth every penny.
Be wary of the list on the Lab School Web site. You want people who are CERTIFIED by the Lab School, not just trained. I could take courses at the Lab School and state, accurately, that I am Lab School-trained. Doesn't mean I'm any good. You might need to hunt a bit before you find the right teacher at the right price who "clicks" with your child. I wasted A LOT of money before we found our current tutor.