Cheap hosting and PHP do go well together, but when you work at a company that has a lot of stuff written in one language, and the whole team is experienced with that same language, there needs to be a legitimate reason to change the whole technology stack. Because it's "cool" or not is generally not a good enough reason - unless it gets to the point where it isn't supported anymore, you can't find employees, the community has dried up, there's nothing new happening with the language, etc. But PHP, despite the problems it does have, it suffers from none of those things. So I don't see a mass exodus happening any time soon.