In a 500$ gift you have more chance to get hats, items or weapons. You can only get Exotic coin in a 500$ present but the chance is less than 5%. You can get a gun in a 500$ present but the chance is less than 1%. You can get a gun in a 300$ but the chance is less than 0.5%. In conclusion, the more expensive the gift is, the chances of getting guns, weapons and items are higher.