It means investors have reasons to doubt about reliability of projects that run their sites on domain names with .io, .info, etc. I am not a technical guy, so I am not sure, but what did you imply that price of a .com site? Millions (really)? I think .com sites for unknown domain names, have cheap price. Blockchain.com is expensive because nowadays blockchain is one of hottest keywords, and crypto, blockchain are future of human civilization.
For other names, ie. Botcoin.com (if I want to run a new project, with a crypto currency, namely Botcoin), I don't think that domain name is expensive.