I try to sell 1 gem with high price and you buy it with that price.
That how we can trade platinum.

no this will not work they precheck all trades

They made it so you can't overprice items to sell them to prevent this

The logic is air tight but there is a certain limit you can sell a gem at. Considering the fact that i know basic gems still sell for max platinum, there is really no reason anyone would do this. You will have to sell your gems for what you'd already sell them for, basically giving away your fg. But hey, go for it