I think it's not visitors, but repeat users which makes it possible and so valuable. This is going to be the next phase of Adtech. Uber has a $500M run rate from ads, Walmart has $2.7B (from the same article), and evidently more and more companies will discover, if you can aggregate traffic to some decent level, you can monetize it with first party data. This advantage is only going to increase once we see Android launch their own version of tracking consent, and Chrome gets rid of cookies. A good horizontal play here is to sell targeting, attribution, and profiling services to all these "aggregators of traffic".
Not sure about the revenues per se, but I think Doordash, Expedia, Robinhood, Airbnb could also potentially generate ad revenue at low cost just based how much traffic (and repeat users) they get