Second, I also made what I consider very good money (for a side-project) from an ebook using a markdown-based approach. All I will say is that I broke six figures in USD and/or Euros.
Third, I happened to use LeanPub to publish incrementally, and that worked very well for me.
Fourth, yes you can charge real money for a technical e-book. I think I have consistently asked for around $30.00, although the interface allowed people to pay less.
I always allowed people to read the book online for free, and people still paid. Did they pay out of a sense of fairness? Did they pay for the convenience of reading an offline copy in iBooks, Kindle, and/or PDF? You be the judge.
Many, many people paid more than the minimum. I have now dropped the minimum to zero, and I still get people paying me more than $20.00.
Lastly, I didn’t get into writing for the money, but I started charging because:
1. People take words more seriously when they cost money. It’s true. It shouldn’t be true, but it’s true.
2. I take writing my words more seriously when I set a goal of asking people for money.
Combining 1 and 2, I felt that whenI set out to charge money for writing a book, I would write a better book. Whether people paid me or not, writing a better book would be better for me, so I couldn’t lose.
Those of you seeking to write for money may have different goals. But those two things drove my decision to charge and to change a non-trivial amount of money.
If you had told me that by charging less, I would make more revenue, I still might not have charged less, because I wanted to force myself psychologically to write a book worth $30.