Complex sentence: The jackpot prize starts at €1,000 and increased by €500 for each time it is not won as a bonus by opening the box containing it within the first three picks.
Split into simpler sentences: The jackpot prize starts at €1,000 and increased by €500 for each time it is not won. To win it as a bonus, the contestant must open the box containing the jackpot within the first three picks.