Grocery Shopping Dilema

Question for the universe.

 Is it just my house or does this scenario happen else where?

    As a teacher payday is once a month and to help save money and time I do most of my grocery shopping once a month. 
     As you can imagine the last week of the month before payday food, mostly snacks and junk foods, are a little scarce around our home. I try to be a fun mom and buy a variety of food. I always try and keep it pretty healthy with lots of grains, fruits and veggies.  
    Okay so here is the problem. As soon as I fill the cupboards with food my children turn into little piggies. They could devour a box of granola bars in an afternoon, a bag of cuties in a weekend, a box of GoGurt in a day, a bag of chips in 5 minutes, a bag or baby carrots in an hour,  a bag of trail mix in a morning, a case of pudding in 3 days...
    You get the idea. I am sure I could set more limits and be the food police but I don't want to. It's not like they are eating a lot of junk it's just that they are eating A LOT.   
    I am not really looking for suggestions to fix the problem. I'm only wondering if it's just my kids or if this is common outside my home.