I highly doubt they're going to make a buck a day from even 1/4 of the userbase from search ads.
Also, they're not being paid every time someone opens their browser. They're paid if someone searches in the Unity lens, sees something they like, clicks on the link, and buys something within 24 hours from Amazon. Amazon's commission rates are < 5% if I remember correctly.
Firefox is more valuable though. They have a revshare agreement with Google and others. People actively use Firefox to search for things, at least a few dozen times a day, not to mention are more apt to click on ads based on their current mindset.
I don't think that same behavior is going to be exhibited in a Unity lens, certainly not with the same frequency. I also doubt the click rate too.
Also, they're not being paid every time someone opens their browser. They're paid if someone searches in the Unity lens, sees something they like, clicks on the link, and buys something within 24 hours from Amazon. Amazon's commission rates are < 5% if I remember correctly.
I think they'll be lucky to make $100k from it.