If you aren't specifying the cost per KW/h and the financial benefit per KW/h, then you are just making assumptions about how the finances work within the context of the current market structure and participants.
None of these things leads to the conclusion that there isn't an arrangement whereby a website visitor can dedicated x seconds to mining and end up paying a reasonable amount in incremental electricity costs for doing so while providing a third-party with a sufficient financial benefit to compensate for the cost of the content consumed/service provided.
Even if it makes sense today, if the approach became commonplace, it would become a lot less effective, as it would require a commensurate and sustained increase of the value of the relevant cryptocurrency for the $0.02/hour that is currently generated by one user to not drop to $0.0002/hour once 100x as many users are participating.
This barely makes sense today, where are your hard numbers showing how this will work if we try to fund journalism by throwing a coinhive script onto nytimes.com?
Tech people love these sorts of things, because it allows us to pretend we've solved a tough social problem (how do we pay for journalism) with a neat cryptographic hashing algorithm, when in reality we've just invented a horribly inefficient way to add hidden micro-transactions to our end user's power bills.
If we are talking about whether a specific existing technology will make this all work, then I agree, I have no hard data to back that up.
But the article is talking about the idea of a cryptocurrency which is mined in the browser as a potential area of exploration for a way to allow a publisher to directly monetize their users electrical resources in return for products or services.
Most of these comments are looking only through the lens of what exists today and assuming that the only implementation is a direct you-mine-coin-you-pay-with-your-coin-who's-value-to-USD-fluctuates. There is no reason a system would need to do that.
It would be just as feasible for a publisher to grant access to the service based on the time the miner is running above some speed threshold not its total cumulative speed, even if the cumulative speed is what is generating value for the publisher. The threshold becomes the fixed price, and fixed prices across customers who provide variable levels of value to a company are common.
I'm not contesting you, I agree, these don't seem like compelling financial transactions. There's just no reason to assume that such a system has to be a mine-and-then-pay-with-what-you-mined-in-USD-equivalent even though that's all that exists today.
More useful would be a 'pay by letting us consume some fixed amount of electricity by doing some mining with your browser'. The difference between what you paid for electricity and what the company is providing you in products/services determines your cash cost, and is different for every person.
That's all POW cryptos are anyway, buying electricity and turning it into a coin that then sells for cash. The worst case would be if you had to pay in cash because its so slow, so then it became just paying with the coin directly, so why not go back further and pay with the electricity directly and let the publisher deal with mining and coins and such?
None of these things leads to the conclusion that there isn't an arrangement whereby a website visitor can dedicated x seconds to mining and end up paying a reasonable amount in incremental electricity costs for doing so while providing a third-party with a sufficient financial benefit to compensate for the cost of the content consumed/service provided.