I think you would find it more useful if you arranged your products down a column, and then have other columns for unit price, quantity, total etc.

In answer to your question, though, perhaps you could have a product 1a, then 1b, 1c etc. for price increases, so you would show 10 items of product 1 sold at £1.30 and 5 items of product 1a at £1.55.

Hope this helps.

Pete