Transferring coins from one wallet to another is basically free for all alt coins and wallets. The part that costs money is the buying and selling one altcoin or another. For that you'll have to go shopping for prices. What I can tell you is....Coinbase is not the cheapest...they charge 1.49% to buy in as opposed to say an app called Uphold that charges .75% for the same transaction.
RE: Is there such a thing as a "best buy" calculator for calculating the cheapest route from fiat to a certain altcoin?