Your actions is one of the advantages of staying long in the system, because most newbies must surely fall for their trap, I believe that their act was intentional to test your fait and to confirm if actually you knew what you are doing however, reading your post is a going to to an eye opener for majority of us to become more observant enough in times like this to avoid being this manipulated by their evil act, indeed it is very essential to say attention before confirming or to continue order, honestly am one of those that gives maximum attention to this regards and reminding this to ourselves is important to enable us not to become a victim of such circumstances.
Only people who are too careless can fall to this expensive withdrawal trap. You don't need to be a senior peson or too experienced user to avoid this trap, just need to be enough careful.
Who don't want to check that how much will you pay before submit your withdrawal request to a centralized exchange, or how much you have to pay for another example with an on chain transaction.
Careful people always check those information and you don't need to be a stingy user to do checking step which relates to how much you will pay or will be charged?