Guarantee of price

Here I will talk about my experience while shopping in India and another European country. While in Europe I used to go to a shopping chain all the time for day to day items as well as items which I may buy once in a while. Once, while buying a bag I found that the price on the display was less than the price that they were charging while billing. When I brought this to their notice they told me do not worry we have guarantee of price, we will check the tag and if it belongs to this product you will be charged the lower price and it happened that way and I had to pay around 5 euros less for and article costing 55 euros. When a similar incident happened in an Indian shopping store where they had displayed a soap bar of 320 gms to be priced 20 rupees and then their machine charged 22 rupees, on bringing the discrepancy to their notice I was told somebody put a wrong display. You may say that it is just 2 rupees. I agree but then at the same price there were other products which I might have taken. And if seen percentage wise it is approximately 10% of the marked price. Also, in one of the stores for glasses it was clearly written in one corner, system prices are final, display prices will not be considered in case of dispute. I am saying this because, the customer should get benefit for wrong display. The logic being that the customer spends some time on the product only when the price is in the budget. If it is out of my budget I will first look for the items in my budget. Then I will go for trials etc. After this, if I find the product is out of my budget then my time spent on that product is either wasted or I go beyond my resources to buy it. Basically this is a crime on the part of the seller to waste my time so he should give me the display price if it is lower. On top of that I am not able to see what is the price quoted in his/her system. Furthermore, if an item is marked lower than the system that means that there is a possibility that the item was sold at a lower price without making any loss. So, if it was not making loss before at the lower price it should not make a loss now. I have even come across shops in Europe where two same items were priced differently. I was told that the lower priced ones are from old stock. If you want you can take that as well. The point I am trying to make is, how do I know the shop is not doing psychological marketing. It is an well known fact that people generally buy a product even if it is priced higher than display since they have spent some time looking at it, comparing it with others and most importantly liked that over the rest of the lot. And I have seen many times in shopping chains in India where the customer is arguing with the cashier that the display price is something else and the cashier calling the guy responsible, who in the end will tell it is a wrong display. To conclude, I would say in any case the customer should get benefit of the wrong display in the form of the lower price of the two between the system and display.