Comment: A rather delayed response. Imagine that a retailer sells chicken for R 30/kg. The retailer has an invoice price for that chicken of R 25/kg meaning a R 5 GP. Written into the supply agreement is that the chicken supplier will pay for various marketing expenses via rebates, shelf fees etc. which costs the supplier R 5/kg.  The chicken supplier nets R 20/kg. If the retailer paid for all the marketing costs themselves the chicken supplier still gets R 20/kg, the retailer still sells the chicken for R 30/kg but the retailer GP is now R 10/kg. This changes the way the retailers books are presented.