I don't think there is a difference between leasing an aircraft and buying it outright in terms of money. But leasing an aircraft is certainly more advantageous than buying, that's why you will never see serious billionaires owning a yatch, they will lease them.... This is because from the moment you buy such an expensive piece of machine every year the asset depreciates in value, eventually, it's going to be worthless...
I know not all planes are leased at the same amount but let's do an average calculation for KQ. So on average KQ spends $142 million ÷ 20 planes = $7 million as lease fees for each plane...
Let's say the plane's life span is 25 years so in 25 years KQ would have paid $177m and if it was 30 years KQ would have paid $210m which is almost about the same price as a Dreamliner....... As we have said, expensive workhorses like that depreciate over time, so if you try to sell it, you would loose alot of money, but if you leased it, and you are not making money off of it, you can just give it back, also if the plane had serious accident that was not really your fault (i.e what happened to Ethiopian flight) you don't cover the cost or suffer the financial loss also since you don't own the plane , you don't pay the insurance premium you only pay a small depreciation fee.... And that is why many airlines preference leasing than owning , so that they can concentrate on the business of flying people, no managing aircrafts
