From experience (and MMM), let's say writing the software takes X mandays of effort.

Making it run, and then run well inside a single organization with that organizations workload is 3x multiplier.

Turning it into something that can be sold to a large number of customers is at least another 3-10x multiplier.

One of the reasons Google is not releasing it is because they have no incentive to invest that 3-10x multiplier.