Different exchanges have also different withdrawal fees as well as into transaction fees to be able to complete the process needed to confirm the transaction you want to make your asset be released from any exchange into your personal crypto wallet you have provided. Not all exchanges have expensive withdrawal fees but most do have which I think also depends on the type of exchange which specially those exchanges that are well-known will surely have high rates of transaction fee. Also, the transaction fee depends on the volatility of the cryptocurrency as far as I can remember. You if you do want to withdraw your asset, be sure to roam around and explore the whole exchange before transferring your asset desired for trading. Assure that once that asset was sold, it can acquire the needed minimum amount withdrawal because it will be non sense once the amount you have sold does not meet up that limit needed to be able to withdraw your asset.