I've recently come across my first skill trainer (Arnick Arduna, in the Gorhart inn). I was looking forward to upping my Detect Hidden skill, but then I saw that I would have to part with around 15K in gold (I didn't even have 1000 gold at the time). My Detect Hidden skill at the time was 2, and I'm wondering if that has anything to do with the steep price.
That is to say, does the cost of training a skill at a trainer increase with the amount of points you already have invested in that skill?