Generally speaking I've always thought the financial cost of running Open Source compared to Closed Source is the same.
Support costs to vendors, salary paid to staff (normally more for OSS geeks), time to switch over from one to another, training and development costs etc.
In addition, it should be pointed out that the article talks of FREE software, rather than OSS. RHEL's is OSS but the cost for a standard licence with standard support is $799. Windows 2008 standard with standard support is $715.
Free software is great, but I wouldn't deploy any important system into any business without dedicating my time to ensure I'm familiar with it (which coming from a OSS background means I'll pick up OSS quicker than MS - and vice-versa), and I'll also never deploy something critical without support behind it - which requires a support contract which both OSS and closed source vendors seem to charge the same for anyway....
Can't see the point personally. May as well stick to what the techies in the department know the best. After all, it's only a tool!