one other way of looking at it is the maintenance cost :
rule n°1 : operate new aircraft because :
- you can re-market them after 6 years with a good value
- you can equalize the maintenance in order to not ground the aircraft for C-Check
- you won't send the engines in shop
- you will have an aircraft free of costly Service Bulletins
- you won't spend money in cabin refurbishment and customization
- you will be in good position to negociate low price if you say "I wan't to buy 120 planes now and take an option for other 120 ones
"
Then, take a full-support PBH agreement for engineering, components and maintenance services with one of the best MRO.
my 2 cents.