Shopping Experiment - Fresh Fruit and Veg

I've watched a lot of programs on TV about food and diets, healthy eating and poverty. You hear a lot of the same comments which go along the lines of how much more expensive it is to eat fresh fruit and vegetables. It doesn't make sense to me. Having read In Defence of Food by Michael Pollen, the reason that companies process food is to "add value". My understanding of that was that they could charge more by doing more to the food so it doesn't make sense that food that hasn't had anything done to it should cost more.

I have been buying our fruit and veg (and eggs) from our local market stall for a while now. Probably since last summer. Last week I did a little experiment. I bought a load of fruit and veg (and eggs) for the week last week and then the next day put the same amounts into mysupermarket.co.uk to try and find out if I was really saving money or not.

So I bought a garlic bulb, a lemon, 700g onions, 900g bananas, 500g new potatoes, 600g courgettes, 1 pineapple, 700g leeks, 500g baby plum tomatoes, 1lb/454g strawberries, 1kg (10) nectarines and six free range eggs. This cost me £11.10 at the market stall.

The mysupermarket website compares four supermarkets, Tesco, Asda, Sainsbury's and Ocado. I chose the cheapest options I could find where there were choices. The outcome was as follows:

Tesco (where I bought my fruit and veg before) £19.39
Asda (the cheapest) £15.10
Sainsbury's £15.62
Ocado £19.23

The overall cheapest option involved going to both Asda (there isn't a local one here) AND Tesco. Here is the end result. 

So at most I saved myself £8.29 and at least £4.52 (if my maths is correct!) and that's not even a week's worth of fruit and veggies for us. I have probably saved myself a fortune over the last 9 or so months not only on the fruit and veg (and eggs) themselves but also on not going to the supermarket as often and therefore not buying things I didn't need as often either. Not only that but I have been eating a lot more fresh fruit and veg because it tastes so much nicer. The stall isn't brilliant about packaging but I can see that the food hasn't been packed with various gases to preserve them because they're doing the packing in front of me. It doesn't appear to have been refrigerated for eternity before being put out either. Not all of the items are local but some are and they are labelled as such so I know exactly where they are from.

Why are the supermarkets charging so much more for fresh fruit and veg? and why doesn't it taste as good? Surely we should be getting tastier food if we pay more for it. Any thoughts?