Most licensed operators charge nothing for a standard withdrawal. Fees, when they exist, usually come from bank wires, currency conversion, or a rule about withdrawing without having wagered your deposit.
The normal case
At a Tier-1 licensed operator, e-wallet and instant-bank withdrawals are free. Charging a player to access their own money is a reputational cost most licensed operators have decided is not worth it.
Where fees do turn up
Bank wires, particularly international SWIFT transfers, can carry a real cost that the operator passes on or absorbs depending on its policy. SEPA transfers within the euro area are usually free.
Currency conversion. If your account is in euro and your bank is in sterling, someone converts, and the spread is a cost even when nobody calls it a fee. Choosing an operator that holds your own currency avoids this entirely, and it is worth more than most bonus offers.
Withdrawing an unwagered deposit. Some operators charge a handling fee if you deposit and then withdraw without placing bets. This exists to stop the site being used as a free money-transfer service, and it is disclosed in the banking terms.
Multiple withdrawals in a short period. A few operators allow one free withdrawal per week or month and charge for extras. This is uncommon at Tier-1 level and more common on lower licence tiers.
How to check before you deposit
The operator's banking or payments page lists fees per method. If you cannot find a fee table, that itself is worth noting: operators with genuinely free withdrawals tend to say so plainly, because it is a selling point.