I always thought the American stock car race system was a good idea, where the winner had to be prepared to sell their car for $1000 or whatever, precisely intended to prevent 'cheque book' development as Simon so neatly puts it.
That was tried years ago Tim and spectacularly failed when the 'LOMBARDS' had enough disposable cash to throw cars away, they would build a race car that was clearly outside of the price limit and when challenged sold it on and replaced it with the next incarnation waiting in the wings. From memory the last club to run a series based on the rule were the 750MC. Some people are sadly so interested in 'Pot Hunting' that they will throw amazing amounts of resources at a 5 bob trophy and their moment in the spotlight.....I have seen it in everything from circuit racing to stage rallies.