I was in my local newsagent in London and saw he had a card of button
cells behind the till which he was selling at £2.99 each.

I recognised the card of cells as one which I can get from my local
pound shop for £1. It contains about 16 cells.

Considering that the pound shop makes a profit then it will already have
raised the price from something like 50p.

I can't say exactly what the mark up is here for the newsagent as he may
get left with oddment batteries that he can't sell but he makes a markup
of about £2.50 on 50p (500%) if he sold just one battery!

His total markup is in the thousands of percent.

Has anyone seen a bigger markup than that?