Charging more to change a ticket than the purchase of a new ticket

Charging more to change a ticket than the purchase of a new ticket

I needed to change a ticket. I am fully aligned that when you change tickets you pay the fee of 402.50. So I needed to change 2x flights 805. The ticket that I purchased was valued at 1637.55. The ones I wanted to change to was 1325.22. Kulula wanted me to pay 1230.50 for change but the value was cheaper than the previous flight. In addition to this booking online with my discovery for a new ticket and ignoring the other one would only cost me R1005.61. After complaining the fee was brought down to R1175.00.. Still cheaper for me to book a new one. I cannot understand why it is so expensive to change a flight within 24 hours of booking when flights are an entire month away.