Build Plumb and Tile - Paint cost

The cost for 20 L of Polvin PVA is R1500 at Build Plumb and Tile and Jacks - while at Rouberto less than 4km away it is R860. How can there be such a mark up !!

When I tried to return the unopened , BPT insisted on the cash slip, even though the sticker on the can and on the Credit Card statement clearly says Build Plumb and Tile.

This is a ver ypoor attitude.