The cheapest way to subscribe to Office 365 is by purchasing a discounted subscription key card—a plastic card with a 25-digit product key printed on the back. As of this writing, you could buy such a card on Amazon for around $68 plus shipping.
Why Should you Buy MS Office 365: If you want access to the Apps Suite, then MS Office 365 is a good option for you as it is providing guaranteed upgrading and updating at a lower cost. You can access all the applications of Office 365 that are installed on your devices such as Windows 10/8.1/7 or MacOS as well.
One awesome feature of Office 365 is that it allows you pick and choose the tools you want. Microsoft has a lot of great business apps and these are regularly released in the Windows Store (many are free!). You can choose to add them to your Office 365 home screen and access them easily from one place.