But why stop there, if you want really cheap servicing at any corner key cutting store then maybe you should confine yourself to quartz movements, Swatch for instance make it nice and easy to change their batteries
Seriously though I think it is rather short sighted to limit yourself to ETA and bearing in mind the imminent restriction on parts you may find that these too become more tricky to service eventually. If cost is the issue then simply take it to a non authorised Rolex specialist who will be able to do it for around half the cost of the authorised guys. It is a little like choosing a Fiat over a Ferrari since the servicing will be simpler.