This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
The supermarkets make miserly returns on turnover and even more miserly returns on capital. One wonders why they even bother, other than for the fact that they are already doing it and can't think of anything else to do.
That is the secret of their success. That they make such pitiful returns yet stay in business. Quite the opposite of the popular belief that supermarkets are driving the dear old "mom'n'pop" (since when did such an abberation become customary in rightpondian English?) stores out of business by making sickeningly huge profits.
Your price difference on one article is great anecdata but hardly useful. That convenience can easily be worth more than heading to the old-fashioned hardware store - the £10 "surcharge" is eaten up in a few miles driving, for example. And you'll find plenty of stuff the friendly neighbourhood hardware store is marking up hugely.
Huge markups are not always insane. It helps keep the doors open. I was at a hardware store a couple of years ago looking for a lightswitch. There was one on the rack. I grabbed it $4. I started to walk away, but something on a bottom shelf caught my eye. Bulk light switches. $0.99 ... I picked it up. I compared it to the carefully packaged item. The same switch. Pretty **** clever that packaging...
Then again, paying $4 to get a switch and install it yourself is still a lot cheaper than calling in the electrician. You can look at the package and say HE TOOK AN extra $3 from me for the honor of throwing away packaging. OR you can say, Hmm. one way I saved $60 over calling in an expert. The other way I saved $57.
Either way though is a lot cheaper than improvising your own from available items short of leaving the wires bare and touching them together when you want to turn on the lights. If you just bend them correctly you can create a spring loaded switch that keeps itself on when touching and apart when not.
Which reminds me of that embarrassing incident 30 minutes or so after I bought the light switch. I installed it, putting the hot lead on one side and the ground on the other. I turned on the light switch and the breaker blew. ****. Three more throws of that switch before I suddenly saw the circuit in front of my eyes. I called myself a few names that would be filtered by this lovely forum, looked around to see if anyone else had seen my awkward idiocy and swapped the leads...
Which reminds me of the time I thought it would be cool to adjust my 220v water heater with my wet hand and a swiss army knife. Never did find that knife. The real irony was the 15 months of training I had just completed that included extensive sections on proper electrical safety precautions.
My colleague and I were at the Ryvita Plant in Poole, installing an American made Mass flow meter.
The design of the power supply part of the PCB was such that it was as easy as anything to short the L and N terminals (not so easy in the UK manufactured version) and that, inadvertently, was what we then did.
There is nothing so embarrassing as the sudden hush of an entire factory shutting down as various mains breakers tripped out and the silence then filled next with the sound of rushing feet heading our way as the plant manager came to see what had shut-down his plant.
The next day when we arrived we found their electrician had been busy and installed our own personal circuit breaker so that if we repeated our misadventure only our bit of kit would be affected.
Mistakes in the home environment are far less embarrassing.
Incidentally, Ryvita is a healthy diet option.... but my colleague (from Manchester) was impressed by the works canteen (something that appears to be disappearing from the British working scene) where breakfast was all things cooked in deep fat fryers.... including black pudding, sausages, bacon, mushrooms etc. The sight of all these staples swimming in fat was almost too much for him.
Possibly the only "food" product for which the packaging is both more nutritious and tastier. Allegedly.
As I didn't mention which food product I assume no writs will be served.