In the US, most major grocers sell big brand products at roughly the same price. There's variance week-to-week as sales come and go, but if you were to plot the prices of P&G, Kraft, or Nestle products at stores in a specific area, there would be strong overlap.

High-end grocery stores do not tend to sell these brands -- You'll find 0 P&G products at a Whole Foods or Fresh Market. So in that sense, they are selling the same exact products.