[LegionMammal978]

From TFA:

> If a spammer needs to spend 0.0001 € in power to access the site only to gain a marginal profit of 0.00005 €, they are losing money with every site access. However, if a ticket scalper needs to spend 0.0001 € in power to buy a ticket that they will later sell at a 200 € profit, this will not stop them.

[tptacek]

And, long before the proof-of-work thing was popularized, people were already farming out high-margin captcha solves to cube farms full of people in Asia.