I don't disagree with this, but I think people sometimes miss the fact that even cheap commodity hardware is way more reliable than most software. Your site may go down more often due to bugs in your HA configuration than it would have gone down because of your VPS dying once a year or so. If you are not a huge operation, the sweet spot for HA is probably something very simple (e.g. two servers behind a load balancer, or something like that).