Tesco charged me �1.38p for two single teabags in their cafeteria. There was no notice telling me of this price...Is it illegal not to not to show the charge? It occured when I bought two teas and put two teabags in each cup When I questioned It they told me it was their policy to make this charge. Their motto is "Every Little Helps"..It does for them !
Let me see would a cup of tea be charged at 69p per chance? I think you'll find that that is on the price list.
In the case you describe it sounds like they are effectively charging you for 2 more cups of tea represented by the 2 extra tea bags. As you clearly tried to abuse the system I reckon their policy is about right. Even if you like your tea like treacle 2 tea bags is too much for 1 cup.
You are paying for a service - a service of a cup of tea, but in Tesco's case they choose to link the price of the service to the provision of the teabag and as much as water as you wish to use. Perfectly reasonable if the price of the tea (service) is marked up on the wall.