Thanks for the comprehensive update.
My intuition (not direct data) based on working in labs for the last 20 years or so is the following. Few labs run on macOS. You can get more bang for your buck elsewhere and far greater ability to upgrade components (which is pretty much impossible now on mac) and ability integrate a wider range of software and hardware. Most labs I am aware of run primarily on Windows (this comes down to many reasons I have mentioned before, so will not repeat here).
However, academia is a massive enclave of macOS users in terms of personal and office machines. These are very often used for developing code (by students through to Profs.).
I would suggest that licensing initially on both macOS and Windows would be by far the most sensible option. You would therefore target a very large % of your users in one go. If that does not work, then I agree with your view r.e. feasibility going on.
I do not think it sensible to start only with macOS as this is, in my experience, not used in labs (see above).
macOS and Windows are the ones to target for the $, in terms of lab based and office and personal machines. Labs will want the most up to date version etc.
Linux is being used more, but my impression is this is still the minority. Whilst I understand your “upgrade to Linux” philosophy, from my experience this is not really reflective of most of your users and the educational / university (and therefore research) sector. PTB also works really well compared to other systems on all operating systems.
Price… I need to give it some more thought, but I think you could ask for more for the “lab license”. Though it also needs to reflect the push to Python across the sector and therefore PsychoPy. If too expensive, folk will just accelerate the move to Python. PTB was pretty much the only game in town in terms of systems folk used for ages, but the landscape has changed with the massive increase in the use of Python. I say this even knowing the superiority of PTB. Just because something is better does not mean folk will use it. Python is the “go to” language these days.
I also think that a “site license” is needed also. Many software systems offer this. Furthermore, there needs to be a mechanism whereby students on courses can use PTB (this can be more then 5 or so). For example, I teach a course with ~30 each year. Also departments would by site licenses for use by all staff and students.
If you would like any help testing the macOS version I might be able to help, all be it in a small way. I use a macOS laptop and the lab is fully of various kit (but the lab runs on Windows).
I will ponder a bit more thoughts on pricing.
To reiterate, I think this is a good move for PTB. All be it I know, not how you would have liked things.
P