You decide what's acceptable to you, yes. But in this case you deemed a $300 hardware device worth the money but you think this software product isn't even wort

You decide what's acceptable to you, yes. But in this case you deemed a $300 hardware device worth the money but you think this software product isn't even worth $20? Mind you, you're not just paying for the build here (which you can do yourself). You're paying for the development and porting work (which you can't easily do yourself and probably costs a lot more than $20).