I have 3 lessons a week but I pay a monthly total because im on a loan pony scheme with my stables. So basically I have 2 30min private lessons a 1 hour long group lesson each week. Private lessons normally cost £30 and group cost £25 but cause of the scheme im on I get them for less. It works out to about £25 for each private and £20 for the group ones. In the group ones we normally either do flatwork, improve our jumping or go out into the jumping fields to test our jumping. In the private ones I do whatever I want to improve on.
I get lessons from my trainer pretty much whenever I want and they're $25 (for 4-H kids, so me) for as long as you need. The other day I was there for an hour and a half, (hour riding, half showmanship). Other days it could be 45 minutes, all depends on what I want to do and how things go.
I take dressage lessons once a week. A half hour private lesson cost $35, but I work in exchange for lessons. I also took a few lesson from a western trainer and it was about $40-50 for a private hour long lesson.
Mine are 55$ for a half hour(I believe..I've never kept track of the time but a half hour pretty standard here, I couldnt find many places that did full hours)
And I go as often as I can afford which is generally twice a week.