How much will this file cost?
To be determined.
What do you think it should cost?
Company hosted file?
Considering there are a few options out there for free I don't see how it has a big value unless you are covering the Google API usage costs. It is also labels only. It will work for some people but have localized value lists is also something most people need.
Put it out for beta testing to a few people and see what response you get on the value. I suppose there are different levels of developers and businesses. Some of them might not know how to do this. Setting up the full core of what I use for labels from scratch realistically takes less than an hour. Two narrow tables and a single script for API use.
A working file that saves a few hours in development is probably worth something...
I currently don't use the Google API but copy a field and paste it into Google's translation field and copy, paste back and parse.