I've been involved in two investigations into migrating from an incumbent on-prem cloud to The Cloud. Once directly, once tangentially. Both times, the conclusion was that The Cloud would almost certainly increase our IT costs, and also submit us to vendor lock-in.
I see The Cloud as being a great play for new companies, and companies with server needs that are both variable and out of phase with everyone else's. Small startups because time is their most precious resource, and picking a major PaaS provider minimizes the time spent making decisions about things that are tangential to the core business. e.g., if you use AWS then you don't have to hesitate for a moment on your object store; it's going to be S3. If you use on-prem cloud, then you'll likely have to burn a few weeks shopping around for vendors and getting it rolled out before you can be up and running. Multiply that cost by every single decision, and you've got a whole lot of distraction hitting you at the most inconvenient possible time.
I see The Cloud as being a great play for new companies, and companies with server needs that are both variable and out of phase with everyone else's. Small startups because time is their most precious resource, and picking a major PaaS provider minimizes the time spent making decisions about things that are tangential to the core business. e.g., if you use AWS then you don't have to hesitate for a moment on your object store; it's going to be S3. If you use on-prem cloud, then you'll likely have to burn a few weeks shopping around for vendors and getting it rolled out before you can be up and running. Multiply that cost by every single decision, and you've got a whole lot of distraction hitting you at the most inconvenient possible time.