The fines are already plenty high, it's just that they are essentially not enforced at all. You could definitely illegally commute everyday in a carpool lane, and expect to maybe get a $409 ticket between 0 and 1 times every 5 years or so.

A $490 ticket every 5 years works out to only $1.88 per week- effectively free for anyone that makes enough money to commute in a car in the first place.