Blynk is up and running since 2015. So it’s here to stay, especially since business side is developing well. We also proved the reliability of the platform with 99.99% uptime (which is public data)
If you are you asking if a $20-30 investment (which is Energy enough to build spaceX monitoring project) will cover you forever? I would love to make such forecasts, but eternity is too abstract for me. On average, life span of the product accordingly to our data is 5-10 years. So it looks like you are pretty much covered. Compare Blynk pricing to other IoT platforms and Blynk would win this comparison too.
What I do think though is that Blynk costs are incomparable with investment in hardware for a “big house” you mentioned. And in IoT world, software costs are usually end up being way higher than the hardware ones. Blynk is very much underpriced for what it delivers. So even supporting the platform for all the years of servicing the community and making complex tech more accessible for anyone is worth investing in (no matter how long it lasts). I’m sure my team deserves that.
Every individual who created account on Blynk can use free Blynk Cloud. We don’t see any reason in making app exporting for individuals as everyone can use Blynk app and it covers ton of use cases for individuals. Can Blynk app be better? — always Yes (that’s why new platform version is on the way).
Standalone apps is a very different service. The lowest plan we offer is $99/month as stated here: Pricing | Blynk - IoT platform for businesses . Buyout terms are also there. Try hiring a freelancer who would code an IoT android app for you and will support it for $99/month and you’ll understand that Blynk is a no brainer.
Not sure what you meant here: “whole Blynk app exported to your app”. Could you please clarify? If you need branded Blynk app (a constructor), then no, it’s not for sale. I mean it can be for sale, but then you would need to acquire Blynk Inc. and it might be expensive 
where does this discovery come from? It should work locally. Please report bug. Thanks.