My Grandma's Cookies Are the Best

No they aren't.  They just have the advantage of being fresh and warm.  If your grandma's cookies were dried, cooled, packaged, and added with preservatives, they would probably taste worse than traditional, packaged, store-bought cookies.  Let me explain with the assistance of a diagram:

First we will place the general positions of your grandma's cookies and store-bought cookies on the arbitrary axis of goodness and awesomeness.  As we can see, your grandma's cookies are better than store-bought ones, but when we apply the equalizing factors of preservation and packaging, your grandma's cookies dip into the "not-awesome-and-not-good" quadrant.  Treating the change in position as a vector, we can apply the same transformation in the opposite direction, thereby proving that your grandma's cookies are in fact inferior to the original quality of store-bought cookies.