I think about this quite often. Perhaps a more effective argument for this effort is social impact (rather than financial savings). The tech industry is reeking havoc upon lower income earners by rapidly increasing the cost of living. Ironically, many of these companies are social minded and have programs to assist those in need from a day-to-day perspective (i.e. free meal, cleanup projects, etc etc). However, the elephant in the room is that they've done far more damage than is possible to rectify via charity.

Which comes back to the social argument: if tech companies proactively migrate these highly paid tech workers to other municipalities, it could significantly reduce the pressure on rent and home prices. The initiative could be sold as a massive goodwill effort to the local community. And, of course, the employees who willingly move away would get rewarded with a much lower cost of living.