The buying fees are a lot less if you buy by using a transfer from your checking account (you provide them with your checking account number and routing number) but it takes 10 days that way. I bought Ethereum that way on Saturday, July 1st. I won't have it in my account until Monday, July 10th. So by paying that way I got it with a fee of 1.49% but I have to wait 10 days. If I'm willing to pay the 4% fee by using a credit card I can get it immediately.
I don't like having to wait for it for a long time because if the price crashes or if it peaks, I can't sell it because it's not in my account yet. This will be the last time I buy that way.