What makes it harder is that many of these exhaust systems are used off road only, on dedicated track bikes. You can get a street legal supersport bike for $10-

What makes it harder is that many of these exhaust systems are used off road only, on dedicated track bikes. You can get a street legal supersport bike for $10-15k new, and with bikes that powerful, changing from a street legal to performance optimized exhaust can make a significant difference. But these supersports are also often used on the streets, just like you see people driving Lamborghinis and Ferraris on the streets (but not often because fast cars are very expensive). Just another thing which makes legislation harder.