Let's recontextualize this - my neighbor wants to spend $5k to remove a safety feature from their car, because they saw a dumb tick tock. Let's say it's ABS breaking, they're just absolutely convinced it's bad

Now I hear about this, and I don't want their stupidity to kill their whole family. I offer to do it for $1k, and instead I actually change their brakes.

Is this ethical? In the end, I didn't honor the words of our agreement, because it was very stupid. It would've been unethical, likely illegal, to do what they asked

I did save them money and prevent them from finding someone who would've done what they asked. I also did work on their car, just not what they thought I did. They're happy with the result, and no longer seeking to remove a system they don't understand

It depends on your ethical framework, but it seems like a stretch to call this theft. The guy in the post provided babysitting and mentorship, which is part of the agreed services. They would probably not have paid so much for what they actually got, but a certain amount of markup is needed to sell the ruse