if you are selling CTP in GTC and want EM,
you can usealy get 60 mil (= 48 mil after the 20% tax) pr CTP, and you can usealy buy EM for 10-35K each = 1 CTP = 1.370 to 4.800 EM
if you are selling EM and want CTP's
I dont sell EM in the GTC, so will go by 1 EM = 35K witch is the price I can see it selling to atm (= 28K after the 20 % tax), and unless you want to be online the last few min of an auction, and make a bit the last sec, it can be hard to get CTP's for less then 50 mil each = 1 CTP = 1785 EM (or 1 ctp = 6.250 EM if you only get 10K pr EM (=8K after tax))
(but trying to sell or sell EM in the GTC is basickly a wast off time, as you can only sell 1000 EM pr trade

, so you will have to do 2.000 trades or more to raice the Cr's needed to buy 1000 CTP's )
the prices in GTC, depend on how many players are selling/buying, how mutch time you want to spendt trying to get good deals by bitting in the last sec before actions end and how long you are willing to wait for a good deal
on a direct trade with a player, you might be able to negotiate better ratios, as neiher off you have to pay the 20% tax you pay in GTC