Depending on the current solutions that are in place, you could tally up the costs for them and compare the difference. Keep in mind you can get up to 10 accounts free. It doesn't include support, but that could be a starting point.
There are many different capabilities Apps brings to a business that can be highly beneficial. You also have to look at what the pain points are and how Apps can resolve those issues. Feel free to shoot me a message with any questions or if you need help with anything.