The phrase "big bag" refers to something large or substantial in size. It can describe an actual bag that is bigger than usual or be used figuratively to suggest something important or significant. Full definition
The bullying tactics he's gotten away with for so long just won't work when there's bigger fish with bigger bags of money to compete with. (sbnation.com)
I just wish it comes in bigger bags because it gets very expensive buying so many bags at once. (royalcanin.com)
I also buy bigger bags and we portion them ourselves to save even more money that way. (makingtimeformommy.com)