The money is in the list!
If someone is serious about their site, not a hobbyist, they night want to consider pumping money into a list. That would involve making an email list and/or build some kind of social media following. However, it probably won't be cheap to do. Also, even with cash, it might not be easy work.
Webscrapers work pretty well to get your own list, but it only works for certain niches. Like if you are trying to pull contact information about a particular business or something.
That would spam people. That's a good way to get killed, lol! The right way is to get them to voluntarily join some list.
Yeah I've done this (in my personal capacity at work anyway not on any sites I've owned but suppose it can translate). We've wanted to collect email addresses on people so we can target them with some specific offers so we used a combination of data analysis and re-targeting to get them to go through our 'funnel' and subscribe to something so we had their email address which we then pretty much just ported elsewhere into our campaigns. Bit harder now with GDPR (In Europe anyway) to just get people on one list and throw them onto another as it all has to be explicit but hey.