You are correct. The math was poorly done. That is the ratio I've seen people actually selling. Does seem a bit cheap but that's probably because they're going to be getting a gem out of you which can be resold again. Overall, it probably comes out about the same. You may think you're getting an incredible deal but if you have to sell a 60k gem for 90k and you're still paying 9k fg, you had to sell the 60k gem in the first place to get the 90k. So realistically you're really paying 9k fg for 30k platinum. I guess that's a better way of looking at it.

I do stand corrected.