Surprisingly Imron has remained somewhat reasonable in cost, but your local paint supplier will mark up accordingly, but depending on color it can currently range from approx $150 to $450 a gallon (jobber price).... first time I used Imron was about 40 years ago when it was new on the paint scene.... a gallon was $70 and the hardener was $30 (full retail price) that was almost a weeks pay back then..LOL!
I bought my first gallon of white in about '77 and that is pretty close to what I remember for cost. I ordered a quart of red last year and it was $275 without the activator. But if you want the best.....