The moment that you start to realistically price the time required it soon adds up if you are trying to earn a living doing it.
Sure, I can make lots of stuff at home for small $ but if I want to earn a living doing it then I have to charge my time at a releastic rate including taxes, trips to stores to buy things (if they cannot deliver), transport costs, packaging costs and so on. Material costs become almost nothing in respect.
That doesn't even begin to cover the cost of product development. To make one decent item I might have to spend time creating 10 rubbish ones. Each one uses materials. Each one takes a lot of time – much more time than would be taken by a production-level manufacture.
When I'm hiring builders for jobs around the house I try and be realistic and when they quote me x I try mentally to work out how much time it would take me to do the job including going to get materials, tidying up and so on and remembering that they need to get here first. If that x is a lot less than the money lost by me not earning money during that time then it makes sense to hire the guy.
Often when I do the sums I work out that he is charging less per hour than I do even if his x seems initially high.
So, maybe $20 is a reasonable amount for a stove. Maybe it isn't. But if he can make one and get a label written and get it shipped in under an hour then he's probably doing well. If he can do it all in under half an hour then fantastic.
Of one thing I can be sure, at $20 he's not going to be the next Donald Trump.
I also know that my first can stove took an hour and was a failure. A 50c failure is still a failure.

