Hello, my name is Ben and it is my pleasure to assist you with your question today.
Whilst I agree that this practice may appear unethical, it is not unlawful. There are often practices in everyday business transactions that may appear unfair or unethical to one party but that does not make them illegal. You will find that many airlines have similar policies, although they would vary from one airline to another. Some will allow flight changes for a specific sum, others will not even allow a name change and if you wanted to amend any of the original booking details you would be expected to purchase a whole new ticket. As long as you were advised of these charges at the time of booking, for example by agreeing to their booking terms and conditions and being given access to them, you would be bound by these terms, including the fees on changing flight details. This has been a practice that has been in operation for years and it is still legal subject to the above conditions.
I'm sorry if this is not necessarily the answer you wanted to hear but I hope you understand I have a duty to explain the law as it actually stands and sometimes this does mean delivering bad news. Please let me know if you need me to clarify anything.
Please let me know if this has answered your query?