This chart is a good design and is working well to get my 2 year old back into a good sleep routine after spending time in hospital. However I do think it is very expensive for what you get. Having used it for a week the 'reusable' stickers are already curling and I'm not convinced how long they will last.
My recommendation would be to make your own, as you can choose the targets and buy your own stickers. I just feel £9.50 is a lot of money for a piece of plastic coated card and 2 sheets of stickers.