That’s why it’s beneficial to give out free code signing certificates to all Mac developers, with lenient terms. Currently, not all non-malware is signed, because some developers can’t or won’t sign up for the Apple Developer Program, either because of the cost or because of the highly restricted terms associated with the App Store, which is inseparable from the Developer ID program.
Malware authors and scammers have already been paying for Apple Developer accounts, and indeed putting their software in the crApp Store as well as distributing externally on the Mac. The price has never been a barrier, because crime does pay!
Price is only a barrier for some honest developers.