So then, buying the cars is a business expense for Oprah, and the value of the cars is taxable income to the recipients?
Buying the car is not a taxable transaction for Oprah. Giving it away for no consideration, though, gives her a business deduction for the value of the car and generates income to the recipient for the value of the car. She will send the recipient a 1099 in the amount of the value and the recipient will have to show that amount on the recipient's tax return. It's the same for game shows. The recipients of those prizes all get 1099s and must treat the value of what they receive as income for tax purposes. Many of them wind up simply selling whatever they won so they can pay the tax.