Honestly there are some transactions that are free from fee. Just like transactions using the coins.ph bitcoin wallet.
Yeap. Just fyi, Coins.ph transactions are "free" because they're off-chain transactions. Basically just a change of balance numbers of Coins.ph's database. This is why the transactions are only free only if it's between two Coins.ph users. Same thing with Coinbase <-> Coinbase transactions.
I'm using the same bitcoin wallet, coins.ph, you can say that the transaction from wallet to wallet is 'free' because @mk4 is right, they are off-chain which means that they are not publicly viewed in the blockchain. However the conversion from cryptocurrency to local currency might be expensive, I've already tried it and suffer from unwanted loss.
To sum up this thread, the cost of fees depends on how immediate you need it, the faster the higher the fee, vice versa. Also the congestion of network will vary every time, so always watch out for the fee before buying and selling.