There is a small flat fee to withdraw crypto to an external wallet.
Since this fee is dynamic and may change, you'll need to check the on a case by case basis fee following the steps below:
1. Tap the account icon;
2. Tap transfer cash or crypto;
3. Tap "Send Crypto out of Voyager"; and
4. Select the asset you would like to withdraw.
The withdrawal fee is listed on the right-hand side of the screen next to your available to withdraw balance.