Assuming it is equally likely to get a 1x up to 5x chest on a Double Dragon Chest promotion, the normal odds spells a 3x chest and a 6x prize because of the "Double".
Suppose the chance of getting a 200 mil prize is 1 in 100,000. When you use your key on a Double Dragon Chest promotion, your chance of obtaining an average of 200 mil gp with a key is 16,667.
It is still very low chance but it is not like the 1 in millions in getting lucky x lucky in obtaining a double pet drops in one kill... and let's not forget the combat pets, the base chance is divided by the number of skills being trained. It means when you are training melee with all attack, strength and defense checked, you only have 1/3 of a chance of the base chance of getting a defense pet.
16-Dec-2018 20:14:54