[sebst]

Storing immutable data without the need of a notary costs money, true. Blockchain is the first concept to bring a decentralized trustless database to the table. Imho it's a bad thing that Bitcoin as a monetary ledger was its first application, but however: A few days ago, someone here came up with an easy to understand implementation of a blockchain-free idea of such a decentralized ledger: https://news.ycombinator.com/item?id=14730354

So, we will see many concepts around trustless transaction verification in future, in the same way Napster has not been the final solution for P2P data share, but eventually led to BitTorrent.