Earlier quoted context omitted.
This is simply not true. I don't think anyone would pay $4 billion for a referral stealing chrome extension anyway
They're paying for the large existing userbase, regardless of how that large userbase was acquired.
Just look at Honey Droplist https://www.joinhoney.com/features/droplist. Let's say that I wanted to buy a product but I think I'd rather buy it at 5% off. Or let's say that I just put it on droplist for no reason and am not that interested to buy it. Honey could literally provide this information to retailers and suggest price drops and email honey users to create demand. Now, when you see a 10% price drop notifications, you being prone to scarcity are so much more likely to buy. And that's why this data is so valuable.
Now on top of this, you got rewards programs, payment splitting programs (https://www.joinhoney.com/honeypay/overview) (which provide yet another advantage, you got a discount but still can't afford to pay, how about you only have to a quarter of the price right now?), a mobile app with 100+ stores integrated in a single app, it adds up!