It is a web wallet to store bitcoin but now using this online wallet is also to costly as they are now charging for incoming and outgoing transaction also. Even storing high coins is not safe as any time they can block your account giving any shit excuses. So it is much better to go with hardware or desktop wallet which is very good and strong in security.
Are you sure that its costly when receiving or incoming bitcoin to your coinbase account?
I never experience that thing i am receiving bitcoin if someone pays me and never seen that they are deducted for every received bitcoin..
Only the sending is asking for the fee and its not honestly costly i think they are just giving the best transaction speed .
And there are people are always want their transaction fast.. so its not good for those people that they want to pay a small fee for every transaction.