A loot doubler doubles the stats of five loot items carried by one of your mob (wiseguys, hired or you). It doubles the attack and defence stats of the five items your mobbie carries ( weapon, armor, vehicle, headgear, and aircraft).
Every time you obtain a loot item or a doubler... your bases are reworked and doublers re-align with the best sheeet (loot) you have right then.. and in all instances will always re-align to the best loot you have/achieve...
Your goal should be to have a doubler for each mobbie, including yourself.
Purchasing/getting a doubler will also get you 20 skills... or is it 10 doubled??? this means there are potentially 70,020 skills available.
Doublers purchased/gotten over 5001 (why would you) won't pay skills..