Varies hugely.
Dressage with a top rider / instructor I pay £45 for 45 minutes. SJ my normal instructor is really cheap (but very good) at £20 but expect to pay up to £60 for others. Plus deisel to get the horse to them.
I had a private with Yogi back in 2000 and that was £60 then but sooooo worth it
i pay £25 for private 45mins with my RI who's a BHS instructor (not normally a fan of BHS/qualifications on paper and tend to go for experience/reputation... but RI is fab!) she comes to me
pay £35 for private 1hr xc lesson with a different RI - includes hire of their xc though. again a fab instructor
Pay £40 per hour for listed BD judge who comes to me. If someone in the yard has a lesson with her before/afterwards the price comes down to £30 for the hour.
I pay between £30 and £35 for an hour with Emma Bailey, on my own horse, plus arena hire depending on where I go to (she arranges a group of us in the same area so usually pay to hire the arena and a stable for a few hours).
I have jumping lessons with my YO which are £10 for 30 mins though I think she charges more for people who aren't liveries. She is BHSAI.
I pay £30 an hour for my regular instructor but she can keep her costs reasonable as she generally teaches a few in a row. I charge £20 per hour for lessons I give, but also offer a half hour for £10 for those at the same livery as me which I find is popular as it makes regular lessons really affordable.