It's mass production when the resources required for development and testing are much smaller than the sales.
For instance, reliability testing for something as complicated as a cell phone should require tens or even hundreds of units. Electrical testing, certifications, developer's units, demos, bench units, betas, it all adds up, and I'd be very surprised if the minimum number isn't in the hundreds. You can always scrimp on testing to save on development cost, but that tends to be a result in (severe) quality problems.