Thank you for the advice and feedback, guys. Much appreciated.
I have been told by several people (including my wife, who has a business degree) that I should cut off the DIY-ers. I get that rationally, if i want to maximize my revenue/profits, it would make sense to stop giving the thing away, etc. but this is not a 100% rational project
At this point I'm too emotionally invested into the "community", and pulling the plug and going 100% commercial just doesn't sit well with me.
I am to a degree pulling a plug when it comes to the Plus version. No matter how I slice it, adding a standalone purchase option doesn't pan out financially. The amount of effort is very high, and my estimate is that the payoff will be pretty low. If I find data that changes my mind, I will reconsider.
My short-term plan is to move the DIY stuff to a separate website (I already have the diy-dro.com domain, so might as well use it for the DIY stuff), update the docs for the ESP32 build (and plaster DO NOT USE across anything MSP430-based) and add disclaimers along the lines "this stuff definitely works; thousands of people use it, so if it doesn't work for you, it's something you did wrong and I can't help you figure it out". I'm not sure this will stop the emails/messages, but I can try.
As far as features, I think that "you pay more, you get more" approach is fair. The free version is not crippled in any way. I.e. I didn't remove any features when the Plus version came out, and it will keep getting more new functionality.
I get that replacing five DIY adapters with new TDA-420 at $300 each is expensive for a hobbyist, but this is a cost/benefit calculation. "Do I get enough functionality in the Plus version to justify $300?". If not, then problem solved.
For a business, this should not be a problem (to start with, the DIY firmware license if "free" for personal use, so technically/legally businesses should not be using DIY adapters).
As I mentioned before, I will have an upgrade path for the second generation glass/quadrature adapters. That will cover close to 80% of the units I sold since 2021 (just need to figure out one last issue with BlueTooth OTA update code and set up the "infrastructure").
Anyway, just thinking out loud mostly.
I'm on vacation in BC at the moment. Waiting my daughter to finish taking shower so we can head out towards Mt. Whistler...
Regards
Yuriy