5. Why do generic products cost less
than national and store brands?

One reason they're cheaper than their national brand counterparts is that they don't have the research, development, and advertising costs, so they're able to skim that off the price. By and large, Marks estimates, store brand grocery store products cost about 25% less than national brands.

A common reason is the advertising cost and packaging. Medicine for example must contain the same active ingredients as name brand. Also to be noted many generic brands are made by the name brand companies and put in different packaging .