i think a lot of it stems from the 'professional speedway rider'.
professional riders requiring more and more equipment, which in turn means more and more wages, then higher admission prices.
the days where you could turn up with a bike on a rack one week, have a practise and be in the team next week, are gone.
the need to have 2 bikes in the pits, both looking identical and imaculate, where does that money come from? so much harder for the 'bloke in the street' to have a go.