I'm not defending EMIREX EXCHANGE.
But, before you used the exchange you should know the policy and other things about the exchange. Their fee is not 50/50, you typed the minimum thats why you only receive half.
They already have the fixed fee, go to check:
https://kb.emirex.com/fees-structure for more information about the fee. One of the example, BTC fee is 0.001 and LTC 0.15 LTC so when you withdraw 0.002, of course, you only receive 50:50 because you are withdrawl with the minimum withdrawl other exchange could be same like this when they have the same fee and minimum withdrawl as EMIREX EXCHANGE.
But, when you withdraw maybe 0.01 BTC you will be receive 0.009 BTC and 1 LTC will be receive 0.85 LTC.
See? I tested type 0.01 and you will receive 0.009 BTC so you are miss understanding about 50/50 fee.
Adjustable fee or not, all depends on the exchange policy some exchange can be adjustable for the fee but some exchange was also have the fixed fee.