My Canadian Friend bought a horse from France and she paid around 9000euro but it depends on how many horses they have in a container when you are flying. And also you should check the quarantine period.
It depends on what company you use and where you want to study in the USA. The 3 points the horses can enter are JFK, MIA, and LAX. Than depending if it’s a Gelding, Mare, or Stallion they go into quarantine Geldings is 3 days, Mares 2-3 weeks, Stallions up to 1 - 3 months. You’ll have to either get a horse transportation company to bring your horse to the barn you are boarding, or picking up the horse yourself which I recommend.
If you have any more questions or concerns feel free to message me. I’ve experience with shipping horses from NL to USA