And bing. don't underestimate Bing. It can be a killer for spam, I have about 75% clicks from bing index.
The thing is - yeah, I do controll the refferer as well. But in my case (not these pages

), it's more usefull, to accept people without refferer as well, cause some browsers won't send em and the EU privacy stuff can be a pain in the ass. I do show em something else, than reffered, but I still monetize em.
It's a gamble of cents per Visitor in the end and the needed performance is less expansive, than visitors per domain.