Vendor lock in is very expensive. At the moment vendor lock in is providing AWS with more profit margin than Amazon's entire retail division. It's more profitable than McDonalds.

It's also A) frequently not all that hard to avoid B) worth doing for reasons other than sheer cost (e.g. flexibility, ability to unblock oneself more easily, ability do deal with bugs by oneself).

If you work in a company that isn't especially worried about hosting costs it's fine (mine isn't, for instance), but most companies are at least somewhat concerned with these costs.