People just think that way because so far mining is the only way it's being done with any level of security. There are a couple of algorithms based on academic research that are being implemented now, and the public hasn't seen it yet.
The event I was referencing turns out to have taken place in Denmark, not Holland, and was auctioning sugar beets, not tulips. They are using secure multiparty computation algorithms to auction sugar beet growing rights to farmers.
https://www.cs.purdue.edu/homes/aliaga/cs197-10/papers/boget...
The paper shows a practical use of secret sharing and secure multiparty computation to discover the market price of a commodity. Not sure how secure it is, but it's interesting.
It's not the same thing as securing consensus of a blockchain ledger. In the paper they have over a thousand participants and 3 (or some small number of) servers. In the blockchain problem, each participant runs his own server. The fault tolerance model is different, and also the blockchain requires continuous consensus.
If you were to run an organization/bank/Paypal clone that maintains a centralized ledger, it would be just as expensive (if not more), because you'd have to hire thousands of employees, compliance officers, lawyers etc. You probably see what I'm getting at.
There's always going to be a price for maintaining accurate accounting ledgers. The only questions is where those expenses are going to be pushed and whether it's going to be your payroll or your power bill.