Ask HN: Free or best priced geocoding service

I am working on a real estate AVM which when deployed at scale will roughly have to geocode 100,000 addresses a day. My only "special" requirement is that I need to be able to save the results in my DB. I know some services don't allow this. I am more concerned about "coverage" than accuracy. If I cannot geocode an address then that property is useless to me. I would prefer to have a larger error in lat/lon than not have a result. But, I am not aware how much of a difference there is in quality between the different options. Error on the order of a full mile (1600 meters) would be problematic but I could live with something like 1/4 - 1/2 mile. Other than that I'd like to minimize the cost while still using a dependable geocoding service. What service would you recommend or do you have experience with?