Goodness, I've never heard of 15,000 for a course.
Why not just go to a university? If you are able to spend a lot of money, I recommend a university with a riding team. This offers a bachelors in Equine Management, Nutrition - whatever you choose, plus riding lessons with professionals.
In my opinion, I would prefer someone who was certified through an active program rather then an online one. It would seem that they were more involved. That's just my opinion and some may just not be able to do anything BUT an online course.
There are several organizations to be certified through. I would eventually like to be certified by usdf, who I think has very high standards to be certified. I would take a usdf cert. Trainer over an uncertified trainer for sure.
Anyway, there is also CHA - Certified Horsemanship Association http://www.cha-ahse.org/
ARIA - American Riding Instructors Assoc. http://www.riding-instructor.com/cer...ion/levels.php
NARHA - North American Riding for the Handicapped Assoc. - http://www.narha.org/
And in case you're interested! USDF - United States Dressage Federation - www.usdf.org
And for hopefully more to choose from: http://www.ohorse.com/organizations/...ication/?reg=7
These organization require time, clinics, involvement and required hours of teaching before being approved. It doesn't mandate that you're a fantastic trainer if your certified, but it certainly showed you had the knowledge and time to pass the standards.