Getchai, it really boils down to what style of pizza you're planning on selling, how long you're willing to bake it for, and how long you're willing to wait between pies. According to my estimates, I'd expect one Chicago thin crust from the PX14 every 20 minutes- 13 minutes to bake, 7 minutes to recover. Barry, what do you think? Does this sound about right?
For NY style, I think you could see a similar turnaround, the only difference being that a 13 minute chicago thin crust might be okay, while a 13 minute NY style pie is pretty bad. You could add a thick stone and trim the bake time a bit, and you'd get less of a wait between the 2nd and 3rd pie, but eventually the stone would be exhausted and you'd have to give it a long time to recover.
I'm not an expert when it comes to Greek style, but I still think 13 minutes would produce a pretty mediocre pie.
In a commercial setting, I don't think three 13" pizzas (of questionable quality) an hour (in the PX14) is going to be very profitable. Other than for rewarming, I don't think the PX14 can cut it. For that matter, I don't think any sub $600 oven can cut it. Barry just bought a Chinese oven for $350 which might be able to produce a semi respectable NY bake time, but it's 220 V, it's entirely unproven, and, without modifications, will most likely have issues with volume. Home ovens generally can't produce commercial volume, and these countertops have a fraction of the power of home ovens.
For tinkerers like Barry, countertops can be a fun challenge. For any kind of commercial setting, though, they're a recipe for failure.