I wouldn't be surprised it's way more than 50% of them. My one is on something like $3/month too. And depending on the design theme you choose (there are huge d

I wouldn't be surprised it's way more than 50% of them. My one is on something like $3/month too. And depending on the design theme you choose (there are huge differences in terms of performance from theme to theme) and as long as you activate a caching plugin, it can easily handle substantial amount of traffic too (such as being on the top of Hacker News for a few hours etc).