it's free for newbies and everyone, ofc it's a trap but freemium model gets people. aws can cost easily few thousands with 2-3 mistakes and clicks. vercel makes you start free then if you grow they bill you 10x-100x aws
They regularly try to get me to join an enterprise plan but no service cutoff threats yet.
That said, I understand people are paying for basically not having to think about infrastructure, and agree that that's theoretically worth money, if they could do it well.