Given that it costs you nothing to upgrade to the latest OS X now, why are people still running the old version?
I have a MacBook Pro made in 2007 that I bought from a friend last year because I needed a Mac, not because I wanted the bragging rights that come with the latest shiny. It came with 10.6 (Snow Leopard) - because he was lazy, and I gave Apple the vast amount of 13 British Pounds to upgrade to 10.8 (again, because I needed it - Xcode didn't like 10.6, and the guy with the latest OS X DVD was on holiday). I did all this only because I needed the stuff there and then an Apple was taking its time with the latest shiny, so I wasn't planning to upgrade to 10.9 if they wanted more money for it. But since they offered it for free I didn't wait long.
If it costs money to upgrade I understand the reluctance - that's what's keeping XP still alive and kicking (it has an even more incentive to stay around as the upgrade costs a hell of a lot more than Apple used to charge), but it's free people! You don't even have to get a cracked copy off the Pirate Bay!
Waiting for the responses that "company policy", "IT department won't approve", bullshit. Kick the IT department in the nuts. They're the ones that will need to fix your Macs when your VPN login details get pastebinned.