With the below example we will illustrate why the even money option over time will result in giving up 4% of your winnings.
To make things simple, let’s assume that you’re sitting at a table where only one deck is being used. If you’ve been dealt blackjack and the dealer is showing an ace, there are 49 unseen cards left in the deck, whereas 15 of these are either 10s or face cards. The are 16 in total (four 10s, four jacks, four queens and four kings), but as your blackjack hand is made up of one of these there are only 15 left.
This means that the dealer will turn over a 10 or a face card 15 times out of 49, which is the same as 30,6% (15/49). Let’s assume that you play out this scenario 49 times, bet €2 each time and always choose the even money option. In such a case you would win €4 each time, which is a €2 net profit. This would result in a total net profit of €98 (€2 net profit * 49 scenarios).
Should you choose not to take the even money option, 15 of these 49 scenarios would result in a push. The remaining 34 would however each lead to a €5 win, which is a €3 net profit. In total this would result in a net profit of €102 (€3 net profit * 34).
As your total win with even money turned out to be €98 and the total win without using the option €102, you would on average lose €4 (€98 – €102) for every €98 bet where the even money option is used. This is the same as a 4% loss (4/98), which means that that you’re giving up 4% of your potential winnings every time the option is used.
The only time that even money is an advantageous option to use is if you would know that more than a third of the unseen cards are either 10s or face cards. With such a knowledge the option would always be a profitable one in the long run as the odds would be in your favour.