Total start-up costs: $150 (proof copies etc.)
We're lucky as programmers that we tend to be able to wrangle LaTeX, and some of us have taste in typography and an ability to write decent prose. This means that the up-front cost of editors, typesetters, cover designers and so on is gone.
The disadvantages compared with my previous (real) publisher are a) no advance and b) no marketing and c) paying for translations to be done. Everything else has been an advantage.
When someone buys my book on Amazon for $35 I get $21. No traditional publisher can beat that.