Leasing vs purchase depends on long term strategy and availability. Lease companies use scale to buy numerous production slots and then can offer them at lease rates comparable to what you would otherwise pay if you borrowed the money and purchased a small run of units at a higher price. If you are an accountant you would know there are certain tax benefits to leasing and to outright purchase. There is also the matter of how long you imagine you will be operating such aircraft, most modern jets are best kept under 10 years old to get the most from the latest efficiency gains. A 20 year old jet probably burns 10-20% more fuel and maintenance and parts costs are again large percentages higher. If you lease, you can sign the contract for 10 years, and then re-lease new machines and keep the fleet age as efficient as possible without having to deal with acquisition and sales costs. You might want to ask Hertz and a few other rental car agencies how their old strategy of purchase and sell vehicles at low kms has gone with their electric cars... I think Hertz is now down 4 straight consecutive losses into the billions due to the junk status of used Teslas and Polestars.
Aviation is one of those places where underlying profits mean nothing. An airline is constantly renewing fleet, brand, staff and everything else. There is never a point where you are just running without some form of change happening, if you are it means things are aging and losing value, so its false numbers, at some point you have to play catch up at more than whatever cost you saved by pinching pennies.