[logn]

Many times the product being sold is so closely related to the actual open source software that they're indistinguishable. For instance, buying RedHat (support). Other times, you're buying the software, under a commercial license. And maybe the most common is, buying the software as a hosted service. In all these cases it's hard to undercut (and offer more value) than the company who has the most expertise and generally copy rights.

However, your example is hardware and I don't know enough to comment on that.