I am comparing two types of products, a commercial product and a commercially supported opensource product and comparing the cost over a certain period.

The commercial product cost includes maintenance fees, disaster recovery site, CPU costs, cost/user. The open source product only has subscriptions fees according to CPU and users.

It is worth knowing that both of these products package-based/'off the shelf', but are two different categories of it. Maintenance fees could be referred to as OPEX costs.

What additional costs should I take into consideration to work out with more precision the cost over a time period?

e.g hardware cost for the production and disaster environments- since two products have different hardware needs as variations of application users

A very similar definition to the open source package can be found here http://cacm.acm.org/magazines/2010/8/96615-seven-principles-for-selecting-software-packages/fulltext

  • The open source product should be free. Or else this is not FOSS! Mar 31 '17 at 2:07
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    @PhilippeOmbredanne what? FOSS doesn’t necessarily imply cost-free, as you surely know — see GNU’s page on the matter for example. Mar 31 '17 at 6:51
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    I think this question is asking about what factors apply when computing total cost of ownership for open source software. TCO includes time your corporate help desk has to spend on support, cost of hardware, etc. However, I don't know how this is different for proprietary versus open software (but I guess it's still a fair question, even if the answer is, "there is no difference in how to evaluate TCO for open source software")
    – apsillers
    Mar 31 '17 at 14:30
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    @StephenKitt While open source software can have a nonzero purchase price, it is weird that the open source version has... subscription fees? ("The open source product only has subscriptions fees according to CPU and users.") OP, what happens if you don't pay the subscription fees? If the answer is, "you lose your right to possess or run the software," then this is certainly not open source. If the answer is, "you lose official support from the vendor," then you should make the clearer in the question.
    – apsillers
    Mar 31 '17 at 14:32
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    @PhilippeOmbredanne OK, free as in libre, sorry for the confusion. I thought you were reacting to the fees associated with the software! Apr 3 '17 at 7:01