Value can be many things of course, and one individual may value certain aspects more than others.  But this is indeed a great question, as too often the natural reflex is that Open Source is free, and free is the cheapest that you can get, and hence it is the best option if it is available.  But there is a lot more to it.

There's things like 'what is the exact definition of Open Source', as there are many flavors of it (even to the extent that people believe that something is Open Source, and then when they start using it in a professional environment they start realizing that they will actually need the paid version of the package, which includes the critical components they need).  Or things like 'what is the real actual cost of the solution' (because in this field of application the license cost is only one of the components that defines the total cost of ownership).

We have a paper coming up that discusses all the pro's and con's when one makes this kind of comparison, and which discusses also the topic of Total Cost of Ownership in more depth.  We'll let you know once that is ready, because I believe this will offer you the information you were looking for.