How would this solve anything? Competing for what? If a bunch of people are competing on say, price, then what's stopping them putting any number they want into the system, or similarly just rejecting every number anyone else puts into the system? They have no aligned interests in the blockchain, and outside of it the legal system already defines their responsibility (i.e. prices must be advertised accurately).

"Blockchain" aka a Git repository is only useful when multiple trusted parties are trying to coordinate a central source of truth without inadvertently removing each others changes.

At which point we can dispense with anything that sounds like cryptocurrency because it's all just signed commits.