Shopping items getting lighter and cost heavier

Everyday shopping is essential for the daily requirements however shopping items tend to get lighter and at the same time cost heavier so the quantities of your shopping items are less of the quality you are getting if for example you bought milk at a supermarket the quantities of the milk is 4 pints and the quality cost £1 and it would last a family of 4 one day then you would need 7 pints of milk at £7 a week this is how shopping is lighter and cost heavier also if you see the supermarket till where they have signs for less than 10 items and the auto express tills where a basket of few items are loaded it's a always few items and more costly.