That's unfortunate. That means when a $100,000 vehicle is sold, presuming a 10% sales tax (e.g. Hayward) then that's $10,000 in sales tax is collected.
That person sells it a few years later, $60,000 and $6000 is collected. Then the $35,000 vehicle is sold and $3,500 collected.
The State / County then collects approx. $20,000 on a $100,000 vehicle? Wow. Not even resellers have to deal with that as the sales tax is generally collected one time, and one time only.
I would presume this is just yet another money grab by Sacramento, and no other private-party purchase is taxed to that extent