Learning is nice (if you have the time), but there's much to be learned in a Linux environment that will take much longer than a week to learn and be proficient with. There's a reason that system managers exist and that IT departments get a lot of funding.
PSM is nice to help get the ball rolling while you learn things I'm sure, but many people don't want to learn that aspect of the computer and just want to focus on business and success. In those cases, a management company is an ideal solution.
As business owners, people need to learn to delegate the tasks that they do not know 1000% - server management is one of those things. If you don't know everything about it, and have secured the holes, you bring in someone else that does know those things.
Personally, as a manager (and owner), I delegate a LOT of things during the day in order to remain focused on the things that I'm good at and contribute to the business success. I have people that are better equipped to handle system configurations, customer service, marketing and SEO and from each (and to each) I contribute, but for the most part they are in the driving seat.
It is nice to learn all aspects of things, but sometimes it's safer to spend the money and let someone else do the task that you may not quite be up to dealing with. Security is a HUGE task, and an incorrect system setup can cause havoc to a business in seconds, and last for days, weeks or even years!
I'd never consider management as a waste, even if they were a backup to the employed staff. More eyes checking usually means increased security/management.