You can lose profit sending trading and withdrawing if you are trading a small amount I have $50 worth of Ferum or FRM it will take $6 to send the whole amount to Bilaxy and after you trade it to Eth and wants to withdraw it you will have to spend $12 to withdraw your Eth,
now that's $18 gas fees for your $50, my only option is to trade it to other altcoins like DGB or Litecoin which offer $4 to $5 fee you still going to lose $11, that's over 20%.
If you have a very small amount of altcoin value it will not match the transfer fee you are using, you better wait until the price is high or wait until it is listed on another exchange, because some exchanges have very cheap shipping fees, or maybe you can use another coin alternative that has low costs like TRX or others, the point is, don't be too hasty for you to sell it on an exchange if you don't know the total transaction fees needed there.