If you want to send a coin, say BTC, from an exchange to another exchange it may be cheaper to convert it into another coin before you send, especially if you are making a low value transfer.
This website nicely summaries the USD withdrawal cost of different coins, by exchange -
https://coinexchangefees.com/So you can see right now it would cost you $8.99 to send BTC from bittrex. Hardly worth it if you only want to transfer say $20, right? But you could convert into say XLM and pay only $0.003 to withdraw.
However, you can also see on the website that there is no withdrawal cost of XLM from certain exchanges, like KuCoin. Therefore, you can't send XLM to KuCoin as it isn't listed there. Instead, you have to find a coin which has withdrawal fees listed on both the exchange you want to send from AND to.
So in this specific example of BTC, Bittrex and KuCoin the cheapest way to transfer is Digibyte $0.0253. A big saving over $8.99!
NB - you open yourself to exchange risk when doing this, i.e the price of your transmitting currency could fall whilst you are transferring (or of course it could gain). This shouldn't be an issue if you are quick, but obviously the larger amount you are transferring the more exposed you are to this risk.
NBB - you will have to pay commission on the trades before and after transfer, but this is normally minimal.
Hope this helps some peeps!