I never trusted paid services more than free ones. I never said that paying for a VPN service is far better than using the free stream. I just said:

The only real difference is that paying users (and their data of course) are less likely to be exposed/sold to some other corporate entities. That's all.

Into that you can count being exposed to advertisements (which can be annoying) or your data (history, identity) is being sold to other 3rd party companies (which isn't less annoying than the first option). And of course, there is never a guarantee how your case will be handled in their system - even if you pay you aren't necessarily completely secure and/or anonymous. But with a paid service you statistically seen can get slightly more chances to being not exposed.

So seen, it's completely irrelevant how a service provider (paid or free of charge) makes money, if you generally distrust them. No, to answer the request, I don't know their exact business model. But do you honestly think that they will show me their exact, real plans for how to dealing with money income? I think not. Because it's simple not lucrative enough for such companies in such a difficult and established market, to be completely honest with the end user. It's sad. But also reading the EULA won't change it much.

And as it seems, those service providers who tried to provide a completely free VPN service and/or nearly-complete anonymous, failed because they couldn't sustain with running the servers anymore and were in need to shut down - because complete comfort (no ads, no data exposure, really free) for the user, is (generally) a disaster for the company that pays the bills for keeping the system running. Or they're still running but can't provide the same comfort that an average (average privacy concerned) person demands.

I agree, maybe the quote is really a bit of a gross simplification but it's not like getting a (free or paid) newspaper with ads inside - when you read such a paper, you are a passive part of the money scheme (you can go for the ad and buy a thing or simply ignore it - because you hold the paper in your hands); but when you're using a VPN service (free or paid), you are the active part of the scheme (you directly interact with the providers goods and use them).