The value prop of migrating to Cloud Service is something that's difficult to commoditize in a way that will resonate with everyone. For example, saving on infrastructure can be high value to some orgs that struggle keeping AEM working efficiently (e.g. particularly those that have a high quantity and velocity of assets) whereas to others it might be minimal savings if their instance is humming and DevOps processes are highly automated.
When considering an upgrade, make sure you're thinking about it more than from purely the technical perspective. Yes, technology licenses and infrastrucure represent meaningful cost, but inefficiencies in your overall content supply chain due to a mess of page templates and components that have not been maintained well over time can be costing you a multiple of the technical costs, yet I don't often see people talk about that aspect.
When you upgrade, a big part of the value prop can (and many times should) be to also modernize/consolidate/clean up. You're already going to be touching everything, regression testing everything, and maybe even reauthoring things depending on the required changes to your components in the upgrade. If you're already going to be doing all that work regardless, it's now only an incremental effort to fully get onto best practices and make the authoring experience simple, delightful and efficient. I'm wrapping up a Cloud Service upgrade right now for a client that did it the right way, and it was awesome to hear an author state "I authored the home page last night because I was having fun" - I assure you they would have never said that about their pre-migration environment.
I recommend everyone take a look at the first half of https://experienceleague.adobe.com/en/docs/events/the-skill-exchange-recordings/aem/aug2023/develope... which focuses on building the value prop of migration.
