I did my Diploma in 2 years at Southbank Institute of Technology (Australia), which, overall, would have cost about $2,500-3,000 with government assistance (it would have added up to around $5,000 without). Each semester of study was about $700 give or take.
We often used the ACSM guidelines as core material for the course. That said, I don't know how well ACSM do at actually teaching Personal Training students. I'm told they offer qualifications through online tests, which is not nearly enough to learn how to train someone. But if you can get a course through them studying in class with a teacher, I suspect it could be worth doing.
Before I started my course, I had about 4 years gym experience, plus a year of experience in martial arts. My course took the approach of assuming every student had come in off the streets and had never even seen a dumbell or heard of a push up. This is good, because taking this approach resulted in them teaching us properly. There's a lot of shorter courses out there, which I think are only really good if you already knew how to do every exercise with good form and how to construct a quality program before you started the course.