I didn't understand witness financials myself until I worked through a few HFs and stoppages. It's pretty simple if explained right. A witness that gets voted into the top is normally seen by the community as the most useful. They usually have large projects and offer things like full nodes or other forms of tech like steem.chat for example. These are big ticket items with a lot of monthly upkeep. In addition, it is ideal that each witness has at least 3 servers. One primary, one backup, and one for testing or secondary backup. Some also have seed servers, which is the same as a witness in size. Those servers must be of good quality to be reliable for a consensus role. They can't be the small MIRA servers (less RAM). There is a level of expenditure and skill (or hiring staff) that must go into a top witness role. For backup witnesses, there is more flexibility in terms of the hardware since the demand is less. However, a backup must invest or the server setup is simply insufficient to actively contribute to a HF or a restart of the chain after an error. Even skill can't save an aging server. But all in all, any setup is still an investment and based on STEEM prices, the good times make up for the bad times but when the bad times are extensive it's not an easy balance. It's more of a beloved hobby type.
There is a lot of confusion about the ninja-mine and about everything in general. There are many underlying factors and dynamics which can be summarized as just community conditioning towards self-censorship over the years. For the first time in years, people who were quiet are coming out and saying what they wanted to say all along.