Cloud really pays back but only for some use cases
I think benefits of cloud gives you depends a lot of what is been deployed there, and how company operates.
1. Who benefits most. Born in a web mobile and SaaS app companies less than 5 years old with no legasy infra or team to run it. Why they use open source software (no licensing constraints) can design the deployment for cloud in mind. Why they benefit. No data centers and more importantly minimal ops staff (cost). Can scale fast if become successful (scalability). Have the bandwidth needed to serve high traffic web apps. (bandwidth)
2. Second group who usually makes returns unless hampered with huge bandwidth costs is more traditional companies entering new markets and projects. Do you really want to build data center in South America as German company just to serve niche market with responsive web commerce solution(global)? Do you want to try figure out how to put together IoT platform rather than use PaaS solution (time to market ). Business-driven IT projects. Do you really want to go through 12 months security review and provisioning process with IT department when you are delivering marketing site that renders HTML with no customer data (time to market)
3. Group who I rarely see to get any benefit or cost savings in the cloud. Enterprise company who deploys traditional enterprise apps with licensing agreements(usually blogs scaling and is not designed to constrain bandwidth usage) to cloud creating these weird VPN accessed mutants(perimeter security) that consume huge amount of bandwidth (cost) do not add any agility or any business value. These are generally done because someone wants to use "cloud". Only industry where I see positive cost cases for these are public sector and financial clients. Why because their own IT cost structure is so bad that anything is better by a mile.
Above opinions are mine, but they been formulated after hundreds of production cloud deployments across industrues, market's and country borders.