Immortality. I used to work for Burson for 4 years and am currently working for Repco as a Catalogue Developer so I know full well what prices stuff fall under.
It really depends what you buy, how big the gap between retail and trade is. At the end of the day, Repco and Burson are primarily aimed at the Trade, with a minor Retail presence. The things we sell to retail are quite often very different to what we sell to trade. Think car wash stuff vs brake pads. Of course the trade stuff is going to be cheaper to the trade, because they are primary spenders and the retail guys dont buy that stuff as often. Things like oil filters and oil there is the smallest difference in pricing.
In the end, its up to the consumer to shop around. The difference between retail and trade allows individual workshops to set a price and compete with other workshops. Sure, you do your own work, thats great. You would probably be able to get trade VERY EASILY from any of these places. Hell, we used to give trade to anyone who had oil on their hands or was wearing overalls.
In regards to the supply chain being affected. I dont know how big the impact will be. When Ford wound back their stuff what 2 years ago? We noticed a very small impact on suppliers. Many places that supply to Ford and Holden, will start supplying to resellers.