[EquitableEngineer]

Your method is good but if they catch you, it is hard to put up a defence if you have a weighed carrot sticker on a pack of steak.
Had a couple of friends who took clearance food labels and put them on steak food packs.
The weights were close enough as there are variances with steak and the technology for selfcheckout tills was quite new at the time.

For more modest savings you can do the following:

1) Weigh organic fruits as regular fruits
2) Choose a similar looking but cheaper pastry
3) Take two products, for example ginger and an expensive exotic fruit, weigh a large amount of the more expensive product that you want as ginger.
Scan some other items meanwhile and later weigh a light amount of ginger to have it as a backup.
If you get caught you can say that you had ginger on your mind and you made a mistake.
This will also be on your bill so it would look more like a genuine mistake.

You are absolutely correct about not really having an excuse for why there is a carrot sticker on a steak packet. Ive done the clearance product reduced sticker switcheroo a few time myself too, works well. I fell like if you are not straight up shoplifting then the workers, even security do not really even care.