Rebalancing cryptoassets on the same exchange (without withdrawing to a wallet [1]) doesn't require on-chain transactions. The fee would be the order fill fee,

Rebalancing cryptoassets on the same exchange (without withdrawing to a wallet [1]) doesn't require on-chain transactions. The fee would be the order fill fee, which for GDAX is 0-0.25%, much less than 2% of the account balance. ([1] For the not-your-keys-not-your-coins crowd: if you don't trust Coinbase with the coins, you can't trust it with the fund either.)