help on price increase on product list ?

hi i have attached a quick test copy of a spreadsheet i am trying to make to keep track of products i make and money from each item .
have worked out how to add it all up and total up money from each product . but what im after help on is if i put my prices up on a item over the course of the year how will i be able to keep track of total ?

as if i change £1.30 in say b4 and there was 10 items then i altered the price to £1.55 and made another 5 items .
how can i do it so it doesnt calculate 15 items @£1.55 instead of 10x£1.30 and 5x£1.55 ? if that makes sense ?

any help would be greatfull