I'm not so sure about that. Lately, I've seen a slew of hosts that use Xen virtualization that are much cheaper than Virtuozzo, and at least on the same level as OpenVZ. It's been known for a while that Xen isn't the fastest VM (it still is pretty speedy though), but I think it's coded with more 'isolation' in mind.

But even if you find a great price on a non-Xen VPS, you have to remember, you may not get your full RAM.