> Though blockchains would probably be too slow for something like this.

This is the key point. Blockchains give a confidence bound on trustworthiness by being too slow moving and computationally expensive to manipulate. This is vital when proving a historical audit trail is correct and immutable.

It just isn't important or applicable for high throughput applications where you just care about local immediate correctness of intermediate results.

To quote one of my other comments in this thread

> Blockchains also don't present a solution to trustworthiness here. In the same way that a wallet being present in a transaction on the blockchain says nothing about the real identity of the parties, nor does it say anything about whether the goods or services the transaction was for were carried out honestly.

We care about whether or not you got ripped off by the guy you gave money to (the GPU you gave data to). We don't care about proving you did actually give them the money at a specific point in time.