What does shopping at multiple stores really save you?

Well, to start with...I have to anyway.  So much of what we eat is brand specific, or our quality standard for x product is only at one store...so it is what it is.
That said, making a list of sale items from each store does save us quite a bit.  Let's look at this week's ads.
A big part of my multi-store reasoning is meat.  I rarely buy less than 6-8 pounds at a time.  Full price boneless skinless chicken breasts $2.99-3.99lb
     If I go to Apple Market this week, 1.69lb.  Given I buy about 8# of these a month, that's a minimum of $10.40 off my grocery bill.  They aren't on sale anywhere else anywhere near that price.  They also have 8# bags of potatoes for 1.99, .99 dozen eggs, and .99 canned pumpkin.  It also makes it convenient to head to a MO side of state line gas station to save me .06 a gallon on gas on my 30+ gallon gas tank in my van.  BUT, I would never do all my shopping at Apple Market.  Their milk is almost $5 a gallon...which leads me back to ALDI.
      Aldi has 1.99 gallon milk.  The cheapest milk I've seen anywhere else is 2.99 g.  We go through 2-3 gallons of milk a week, roughly 12 gallons a month.  So on milk alone, we save a minimum of $12 a month at ALDI.  Their rice happens to be my favorite kind, but it only saves us about .40 on 2lbs.  Their canned pineapple cannot be beat for price or flavor.  Their produce is hit and miss.  Sometimes great stuff for very cheap, but sometimes scary.  Their 1.49 lb ground turkey rolls are one of our non-sale meats we rely on, but I will pay the extra for ground beef on sale to make Mr. Man happy, so that means this time I'll probably have to go across the street to Price Chopper.
     Price Chopper has the ground beast Mr. Man likes at 1.99lb, and the reason I can afford it is the money I saved on milk and chicken elsewhere.  It also has fairly reliable produce at decent prices.  This week it's 1.29lb apples, 1.99 whole pineapple, and .79lb sweet potatoes.  Our bonus items are the 2.49 name-brand oil(usually 3.50ish, generics smoke more and have stronger flavor),  and 1.69 brown sugar, (which 2.19 is the next cheapest for C&H.)
     I usually need to go to Wal-Mart for a few things, like paper plates (cheaper than ALDI,) soy milk boxes for lunches ( about $2 a week savings), the yogurt the boys will eat, (about 1.20 a week in savings), some cereal, (about 1.50 a box difference on the ones we get there, unless on sale w/ coupon somewhere else)....
    Throw in the stuff we have to get at Sams, like canned diced tomatoes,dishwasher,detergent,etc.  Then I really have to hit Hy-vee or WHole foods too because of their gluten free selections, and you can see how I easily end up at about five stores within 24 hours.  This is also why we coordinate our main shopping to be every other week. 
    If I could shop at just one store, it would probably be Hy-vee.  The 1.69 chicken breasts would be 3.99.  They eggs would be 1.99 for 18 on sale.  The rice about .50 more.  The milk, $4 a gallon.  The potatoes, 2.49 for 5 lbs, so to get 8# I'd have to buy 10# for $5.  Oil, about 3.49, brown sugar 2.19.  The soy milk boxes would be about $8 more for the month.  The cereal, $2 more a box, at least $10 a month.  The yogurt, about $1.50 more a week or $6 a month.  So the monthly payment for just one store?   Well, let's just say milk alone would be $25 a month more.  Just the milk pays for gas.