TCO and human hours for large deployments

[Lance Reed]

I am working out the Total Cost for a large (er, scalable...) mogilefs 
deployment.  The numbers for hardware are relatively easy depending on 
design.  However, like all opensource initiatives, calculating the time 
/ resources for administration by humans is tricky until you do it for 
awhile.  Our company has plenty of experience using OpenSource tools for 
the majority of our needs, with the proprietary solution thrown in where 
applicable.  So I was wondering if anyone who is attempting to setup a 
mogilefs storage setup, or who is using one now could shed some light on 
the subject.  I figured initially, on a new deployment, about 60% of a 
single Administrators time would be taken up to maintain a large 
mogilefs cluster.  I figure design and implementation would take much 
more than that (maybe 2 or 3 people to save time).  I am comparing this 
to a couple proprietary solutions we have been looking at that are known 
to scale well into multi TB or even PB setup that are basically Scalable 
NAS solutions that use a "brick" mentality.  The theory being that you 
pay upfront for stability or support if needed.  But I am wondering if 
say 60% for the first year of learning how to maintain and grow a 
production mogilefs is close or not.  Too high / low?

Any thoughts or real work data would be great.

Thanks all!!