Honestly I'd be highly surprised if producing a single pair of glasses would take more than an hour end-to-end, as long as you aren't grinding them by hand. Wit

Honestly I'd be highly surprised if producing a single pair of glasses would take more than an hour end-to-end, as long as you aren't grinding them by hand. With modern plastic lenses it's basically a CNC machining operation followed by a couple of polishing steps. There's no reason you can't do a pair with basically no automation aside from the CNC in an hour easily. And that includes sticking them in a lensmeter to check if the prescription matches for QA. Of course more complex things such as antireflective coatings add a sputtering step to the process which might be a bit much to expect a shop to do in-house.