There are more options for a business type purpose, such as having many different prices: £3.80, £9.40, £15.10, £7.90
As well as having these prices, you need to check what comes with it, for example the more expensive it is, the more you can get for it. So you are actually paying for a lot, you can invest all the other microsoft apps, such as powerpoint, word, and the other ones.
£3.80 is basic.
£9.40 is standard
£15.10 is premium
But the £7.90 is just the apps.