I am not the product of a free extension, whatever that means. I am a NextDNS subscriber. That makes me just as much their customer as my ISP's.
Besides, I don't know what a paying-customer relationship has to do with trust. I could just as easily be betrayed by someone I'm paying. For example, GrubHub drivers have a chronic problem of "losing" my drinks, despite being promised a tip and wages. I have to go chase refunds every day for these "mistakes". I'm a paying customer, yet I can't trust them to get my order right.