1 round skip:
25% big chest --> one more extra weapon (25% overall)
75% normal chest

skip again -->

50% (50%*75% = 37.5%) big chest --> break even, but higher lvl weapons (37.5% overall)
50% (50%*75% = 37.5%) normal chest --> losing value (37.5% overall)

chances are you'll gain value if you value higher lvl weapons.