A lot of places as I'm living tai South-Eastern Asia, where 3 billion people but only on income 2000 usd/year. And this opinion is also eager to submit to you the administrator Blynk:
- Private users will never be able to pay much, especially in countries outside US/EU (China, India, South America, Russia e tc).. $2,5 / month is definitely too much for them. I suppose, the maximum ONE-TIME fee a user can pay to include Blynk into his project is equal to 0,2-0,5 of other hardware costs, that means Arduino/Raspberry board and peripherials. If you set higher price, you'll definitely kill yor Blynk before it gets really popular (1M downloads), because people simply won't evers start projects requiring Blynk. You should go WhatsApp-way (you know, they asked $1/year and got millions of users).
- On the contrary, commercial users could pay even more. There are plenty of commercial applications Blynk is suitabe for. You just need to offer a very stable, robust, extremly well documented platform, going behind handheld devices, with lots of api's allowing it to incorporate into commercial apps. Make commercial-only widgets with functions a private user will never need. And yes, that's what you could ask to pay for. And they will, because they'll be getting profit out of using Blynk.
So the bottom line: give unlimited private version to everybody for as low price as you can, this will give your success like Arduino of WhatsApp. 10k users paying 2,5/month are not better than 1M users paying 1$/year. The idea to make expirable free tokens as very good. An amateur will be able to get a new each month and re-flash the device.. A professional business user will definitely prefer a paid perpetual token..