I feel like cost and power are more of an issue than reliability. I'm sure everyone knows you can't run a Sushi Box pedal on a standard Boss adapter, you need something beefier, which is why a lot of tube pedals have their own power supply (Blackstar uses a 19V adapter with theirs?) which a lot of people (myself included) don't like. Also aside from the cost of parts, which is not trivial, for a company to design a tube pedal they need an engineer/team of engineers comfortable enough to design a good product, and engineer labor is not cheap, so the company has to recoup the cost of development in the price of the pedal.
So how do I do it? 1) undervalue my labor. I generally don't even consider the time spent in development in the cost of a pedal, just cost of parts + time to build. When I value my time spent building I charge between 1/2 and 1/3 of what I make at my day job. 2) low overhead. I have a good day job, pedals aren't what pays the bills (though in the past few months you guys have paid off my wife's car and all of our credit card debt, so thanks for that

).