How much money per customer do cell providers spend on advertising?

Specific amounts are confidential within the various provider companies. Experience would seem to indicate that the "acquisition cost" per customer is likely to be $200-$400. Of course, it matters whether or not you are including the wholesale cost of a "free phone." Usually a company gives a credit of about $150-$200 on a 2 year contract toward a new telephone. The company expects to recover this cost over the course of the contract.

A very simple phone could cost a company around $50 wholesale, but many of the fancy phones out there these days cost in the hundreds. Customers may be able to purchase "knock off" phones, typically from Asia, with prices much, much lower than name-brand phones that have been developed for and tested on a particular company's network, thus giving the impression that "free phones" don't cost a company much at all.