Our PTO pays for transportation only. Grades 2-5 use charter buses because of the distance they travel.They run $600 - $1,000 for each bus. Each grade needs 3 buses. We spend $10,000 each year. The field trips are the same each year. Grades K & 1 use school buses and we pay for their use and for the drivers.
Our PTO pays for 1 class trip for each grade level, per year. We try to keep it the same each grade so children aren't going to the same place year after years. Each grade level gets to choose their trip. Most have kept it the same each years, like 1st grade always goes to the pumpkin patch, 4th grade goes to the Quiet Valley farm in the Poconos, etc. A couple we had to change due to transportation or time problems. This seems to work out fine. Each trip usually cost between $300.00 to $500.00 depending on the class size. 6th grade we handle different as they get the most expensive trip. We give them so much and they have to raise the rest.
The student council at our middle school is in charge of our annual magazine sale. This raises enough money for some of the field trip expenses, but the parents are always asked to pitch in a pretty hefty amount too, usually at leat $10 per trip.
I'm always happy if they even get to go on ANY field trips. Seems to be an activity that seldom happens these days because of the high transportation costs and budget shortfalls.
Our PTO pays for all of the field trips for our K-3 graders. It varies year to year, but it is pretty safe to say we pay upwards of $10 per student. If we did not supplement then the cost would go to the parents.