Ok so I was talking to another Halfling and he mentioned that his cost for raising agility by one rank was too high. I went and checked my own and saw that indeed it was for me too. The equation is:
(current rank X 3 ) + [(current rank X racial mod)/2] so say I was raising mine from 37 to 38, it would be 37 X 3=111
37X-2=-74/2=-37
111+ -37= 74

So it should cost me 74 tdps to raise my agility to 38. However:
You consult with the teachers and together decide that it will take 75 moon cycles until you successfully gain a rank in agility. There is also a fee of 150 Kronars to complete this training.

So it is off by one. The same happened to the other Halfling. His was off by one when he wanted to raise it from 15 to 16. Are we getting short changed on TDPs?

-Maliase

ps- This only seemed to happen with Agility. All of the other TDPs worked out fine.