This is often tightly coupled to hosting providers. I've worked before at a company where we did hosting + full sysadmin services for high-performance computing

This is often tightly coupled to hosting providers. I've worked before at a company where we did hosting + full sysadmin services for high-performance computing. The big challenges included finding talent (good sysadmins are not easy to find), keeping the right balance between employees and customers (you always need more employees than you think), and setting realistic expectations for pricing. When coupled with hosting, customers are often unprepared for how much extra management really does cost... If decoupled, would be interesting to see how you could price it.