When one lift is down, residents will feel painful already, and when two lifts are down, they would question why they stay there, and the worst if you are at 35th floor, you have no other option.... 4 lifts are required as minimum. Not worth cutting costs on number of lifts.

Lift is actually not expensive... 3 lifts is is way too less. Imagine 1 breakdown/maintenance, 1 use by the cleaner/contractor.... everyone will need to share 1 lift... nightmare.