TANSTAAFL = There ain't no such thing as a free lunch... or breakfast sandwich in this case.
In Canada (and possibly elsewhere?) McDonalds is having a huge promotion today and tomorrow (February 9-10, 2011) of their new Breakfast Buttermilk Biscuit Sandwiches..... "free", one to a customer, one per day.
...*Remember that for economists, "there's no such thing as a free lunch", and that applies equally to "free" biscuit breakfast sandwiches. The scarce resources used to produce those sandwiches have alternative uses, and hence involve an opportunity cost.
That's Doc who, by the way, is not a fan of the breakfast biscuit sandwiches.
When the price of a good is below it's equilibrium price, shortages form and that leads to non-price rationing. From comments over at Facebook regarding Doc's post.
As I walked by McDonalds on the way to work, cars were lined up down the street and people were packed into the store to land their "free" biscuit. I am truly amazed at what people will do to satisfy the illusion they are getting something for free.
These people are giving up their time to wait in line to get something for which they must sacrifice no money. But it ain't no free breakfast buttermilk biscuit sandwich. TANSTAAFBBBS.
Personally, I'm more-or-less indifferent about McDonald's buttermilk biscuit sandwiches. I prefer the McMuffins and I do not care at all for the McGriddle sandwiches. I like the taste of bacon, eggs, and cheese together and I love pancakes and syrup. But I do not like all these flavors in one bite. I do not like it, Sam I Am.
Now for your consumer surplus example. One of our local McDonald's is giving away a small coffee at no charge until Valentine's Day. I was willing to pay whatever the normal cost is, so I experienced consumer surplus. And I didn't need to wait in line.