It's not true that you only pay for the support. Many open source packages are fee based and the installation and setup challenges can be considerable. Open source does not necessarily equate to free - the source may be open, but you still pay for some stuff, especially enterprise type applications. This is poorly understood in the industry. Business leaders need to be extremely careful when implementing blanket policy changes.
I have no particular agenda for proprietary vs. open source software in the business world. I believe in using whatever gets the job done most efficiently for business. Unfortunately, open source has become a bit of a buzzword lately and most non-technical business leaders see it as a panacea to rid themselves of IT charges, particularly licensing.
I'm all for building new ventures on open source and phasing in open source solutions where viable, however, I've seen huge wastage of money and resources because of the adoption of open source just for the sake of open source. One example currently is a very large organisation that is currently moving to the open source platform and has decreed that every system in the mammoth organisation must convert to an open source (but paid for) database platform. They are spending an untold fortune converting literally thousands of software packages and custom developed solutions to the new database platform - not to mention the fat fees they are being charged just for consultants to export the data out of the old platform into the new. Virtually every project in the organisation has been set back months.
I guess my point is, if what you've got is working, don't fix it just for the sake of being open source. And be very careful when you work out the costs of open source, as they are not as obvious as with proprietary software. It's not just support - installation can be significantly longer and a surprising number of open source packages are fee based for commercial environments.