This is more akin to if you sold a fatty food in a supermarket and someone died from being overweight.
Radicalizing someone to do this isn’t a crime. Freedom of speech isn’t absolute but unless someone gives them actual orders it would still be protected.
Don’t apply UK’s lack of freedom of speech in American courts.
I don’t know the right price point, but 1 dollar a month probably would have worked for most people. It just wasn’t enough because they probably can make more than 1 by spoon feeding you ads now.