The jewelry store we went to told us that there are no real standards for cut except for the round cut.
They also gave us the acceptable percentages for the parts of the round cut stone.
I know that my boy bargained on the price of the stone. He bought it loose and had them set it. He actually didn't ike any of what they had in the store so they shipped in more stones from NY and he picked from one of those.
My stone has incredible fire. It's an I in color, which is still "Near colorless." My boy said he put it next to the D stones and couldn't tell a difference.
I love my ring and it gets a lot of attention. But, it really doesn't make a difference in the long run - the real gem that I got/am getting is my boy