When I wanted to change my return trip from BKK to Seattle because Singapore Airlines had changed the Bangkok to Singapore segment by 3 hours and 45 minutes, Singapore Airlines said to contact Budgetair, the third party agency from whom I had bought my ticket. They said it would cost me $1,650 to change a ticket that I bought for $674. I ended up buying another one way ticket to get home and am suing Singapore airlines and Budgetair $880 for the price of that ticket. Singapore airlines rationale in your and my case is to make a lot more money. While not every customer is paying the difference, enough are to justify the policy.