This is the same argument as from the IRS propaganda-for-kids page, and it's flawed.
Your average billionaire probably won't be buying that $30,000 car -- he'll be buying a $150,000 car or a $50,000,000 jet. How much tax did you pay on your ~$80,000 home? How much did BillG pay on his $65,000,000+ home? His property taxes alone for the first year were close to $600,000.
On a more down-to-earth level, I believe the IRS used the example both rich and poor taxed the same on a cheap tire. Poor average guy, he paid a bigger percentage of his income on taxes when buying that tire. However the truth is that the average guy will buy a $50 tire for his Neon, but the Porsche driver will be paying over $300 for a Pirelli PZero that will last for half as many miles.
The sales tax may or may not be great for the economy depending on what economic school you're in: it'll encourage saving and discourage spending.
Q, Which is exactly why it is a bad system. Tax systems should NOT be used to further some socialist agenda over another. Peace and love, George.