[runeks]

> So while you can pay to have CAPTCHAs solved, you actually DO have to pay and can't just steal your way in, so it means your target has to be more valuable.

None of these things you listed above are available for free. They all require either effort to obtain or paying someone to do the work.

[remram]

Someone did the math down thread: https://news.ycombinator.com/item?id=37056504

Unless you set your challenge to many minutes of work, you are not competitive with the human-centric solutions.