Gdax saves you from a lots of fees! I also was buying BTC on coinbase platform and I remember my first attempt at 100$ I had 3$ fee only for purchase and when I wanted to transfer them to another wallet, I noticed that the fees was much more than 3$ so I did my research and hopefully I found this method with Gdax and I have to say that is very useful and you save a lot of money for someone that doesn t have a lot BTC and the amount of the transaction is really small.