Justify an upgrade to ECC 6.0

Hi,

We are currently running ECC 5.0 and I've been tasked to create a document to justify an upgrade to ECC 6.0. I thought this would be a straight forward exercise to find ROI associated to an upgrade but it is turning out to be more difficult than I imagined!

Besides maintenance implications does anyone know of a good source of information around ROI on an ECC 6.0 upgrade?

Thanks.