In any form of racing, whether spec, open, GT, On road .... Cost and maintenance will always be part of it, and it generally follows, the faster it goes, the more expensive everything it will be.
There is no such thing as maintenance free racing when at a competitive level be is spec, open or limited rules.
Spec class would be ideal though for local club races cause it kinda makes initial cost fixed and maintenance costs/running costs less.
Open class should also be available for the sick guys like me!
Best would be for IFMAR, ROAR or whatever international ruling body to approve certain model engines of different brand for an approved international spec class motor and dictate maximum SRP price...