> candidate time is free and manager time is massively expensive
This is a naive view of the proceedings. Why not hire literally the first person that applies? That would reduce your cost even further.
The point is to figure out who would be good at making you money. The question is, does an ai chatbot wasting your prospective candidates time make you more, or less, likely to find people good at that? Perhaps it reduces the amount of cost reviewing applications, but I imagine it also drives away a good number of the better candidates, those that have more options, away. If you're cutting corners and cost this much, why are you even hiring? surely the point of the exercise is looking towards future growth.
Naturally, there is also a limit to that line of thinking also - spending weeks reviewing each one of the ten thousand applications to your junior developer role wouldn't be the most efficient way to grow. But surely there are better filtering methods you can think of than this, which is imo the equivalent of planning on reducing the number of candidates by lining them up in a room for hours in sweltering heat and hurling verbal abuse at them until only a couple of the wretched ones without a shred of dignity are left