explanation of “so lucky you could die”

Just like in the US, many brands hold promotional contests to win free products, among other amazing prizes.  Probably best known for doing this are producers of bottled soft drinks like coke, sprite, iced green tea, and iced black (or lemon) tea.  Some producers use the tag line “zai lai yi ping” to announce the promotion, which is also the phrase they print on the inside of bottle caps to indicate that the bottle is a winner.