After Burner, although I agree with your analogy to a point, I have to point out that a broken down motorist is not necessarily in a position to take those steps. When I worked for the AA, I was instructed to carry batteries which I believed to be overpriced. I don't think I ever sold one as I knew full well that the batteries I carried had to be sold at around 50% more than I knew I could source one elsewhere. I also believe that there was an arrangement between the AA and some sources that parts supplied via the AA would attract a higher price than if sold to a person walking in off the street. I don't know if this practice still stands.
I do agree that RAC and AA now being commercial enterprises will do what they can to make a profit, but I do not accept that all their actions are correct, at least ethically.
The RAC website quotes £100.99 for an Exide battery to fit my car, with free fitting and a 3 (not 5) year guarantee.
I can buy the same battery (Exide EB620) for £64.98, with next-day delivery and 3 year guarantee, and fit it myself for free, saving £36.
On the other hand, the last time I actually needed one, I was happy to pay the RAC. The car was stuck at home, and the alternative would have been either to wait a day for delivery, or take a taxi to Halfords and back. Plus a trip to the dump with the old battery.
Convenience has a price!