I got this from coinbase support:
Using our wallet services to receive and store digital currency is free.
Your conversion rate for buying or selling digital currency through our Conversion Service is calculated as the market rate of the digital currency on Coinbases GDAX platform, plus a spread of up to 50 basis points. The final rate will be quoted to you before you complete your transaction.
We charge fees to use the Conversion Service, which vary based on your location and payment method. In some cases we may charge a fee on transfers to and from your bank account. We will always notify you of the service fee that applies to your transaction, both at the time of the transaction and in each receipt we issue to you.
obviously you can receive bitcoin for free. So my advice will be to store enough bitcoin before trying to transfer or spend. That's the only way not to feel the impact of the fees.