Pricing Emeralds

[andrescolombia]

I've asked this question to many people and nobody have answered me. Why??? I don't know, but I'm still looking for it.

I want to buy some emeralds from a seller in Colombia, but asking for prices I've found very different prices for very similar emeralds.

Does somebody knows if a table, chart or scale has been designed to price emeralds?

For instance, "a 3ct. emerald, VS1, Bg, medium color will not cost more than $x".

Thanks to all the gems field!!!