That is correct, your local VMware SE or Channel Partner can assist with an ROI, but from a high level there are several ways NSX can provide a return on investment. Microsegmentation vs. traditional HW firewalls. By using NSX you can "right-size" your physical firewall and offload east-west firewalling to NSX. There is a CAPEX savings there. For logical routing, switching, load balancing and other physical network functions, NSX can automate those tasks and therefore provide OPEX savings from having to manually configure the physical network. Also, many customers air gap DMZ, test/dev, or PCI zones and have under provisioned hosts. NSX can logically segment those networks thereby save on underlying switch ports as well as host servers. These are just a few of the high level benefits that can be quantified. There are many more as NSX is the platform for a modern day data center. Check with your local SE to help.