Generally speaking, think of it this way: I can buy from multiple vendors, some of which show up in some magic quadrant report which my CTO reads. Why would I pick your product instead?
The usual good reasons are that you can provide me with professional services to do the integration, educate users, participate in project delivery, etc, but essentially that you are able to somehow remove some degree of risk for me and the company. You will most likely need to show some evidence of compliance to best practices for security, data privacy and segregation.... well depends on what you product does and what company you are selling to, for sure, but think of the PCI and Data Protection Act's guidelines at a bare minimum even if not directly applicable.
Specifically around support, I will want to know what are your SLAs including MTTR, MTBF and availability to begin with, and then I expect you to sell me 2 or 3 support coverage contracts (bronze, silver, gold) and offer me a possibility to design my own (platinum) if I need better. See Google's GCE page for instance: https://cloud.google.com/support/
Hope this helps you somewhat, but without knowing more it will be hard for me to get into any more detail.