Say someone won $50,000 on Deal or No Deal how much or what percentage of that do they actually get to keep after all expenses?

UNITED STATES:

"The short answer to this question is that it depends on your state, and how much you've won.

If you win money on a game show you do have to pay income tax on the winnings.

On your tax return you would file game show winnings under Miscellaneous Income. You will also receive a 1099 tax form from the entity that awarded you the cash prize. For example, under the rules section of Who Wants To Be A Millionaire, it explains a contestant will receive a 1099 form to declare taxable winnings on prizes valued at $600 or more. That doesn't mean that if you win less than $600 you are exempt from declaring it on your tax return. It simply means that they may not send you a 1099, but according to the IRS even winnings as low as $50 must be declared as taxable income.

How much you have to pay depends on certain factors. One is whether or not your state charges an income tax. Seven states don't charge income tax, so if you win a game show while living in one of those states, you'll be in better shape. Second, what tax bracket will you fall into after winning your money? If you win a game show, you might make a considerably higher amount than your annual salary. This new injection of cash could then put you in a higher tax bracket.

Let's say you won $25 million in the lottery in New York City. City and state taxes add up to 12.7% (rounded up to the nearest tenth). Add 25% for Federal taxes, which comes to 37.7% or $9.4 million that you will have to pay in taxes. This is also true for winnings from a game show. The only difference with the lottery, again, comes down to the state. Certain states do not tax you for lottery winnings, such as California. If you live there you can expect to only pay Federal taxes. So there you would only pay 25%, or $6.25 million in taxes."

http://www.nerdwallet.com/blog/finance/fun/pay-taxes-game-show-winnings/

AUSTRALIA:

If it's on the Australian version then you pay no tax. Winnings from game shows or gambling are not taxed in Australia (unless you are deemed to be a professional gambler).

https://www.ato.gov.au/Individuals/Income-and-deductions/Income-you-must-declare/Other-income/