In poker, the fifty cent juice per hand is called the rake; money that the casino charges for each hand of poker. It is usually a percentage or flat fee of the pot - in this case fifty cents from each players hand - after each round of betting.
Normally, this fee is tolerable in poker because players do not bet against the house, but against each other. How else is the casino going to pay for their employees, playing tables and neon lights?
However, you were hoodwinked, okay, suckered, into giving up the additional fifty cents per hand because 3-card poker DOES have a built-in casino advantage.
Even if you were to employ a sound betting strategy like not making the "play" wager unless your hand consists of at least a queen, six, and a four in your hand, the house edge on the "ante" wager is about 2.1%, with the "pair plus" slightly higher at 2.3%.
A bearable casino advantage, yes, but it does not merit you giving the casino an additional fifty cents per hand.
Giving them their supplementary fifty cents is akin to being suckered into making a sucker bet, which, if you do not know the difference, makes you the sucker.