I will try to address these:

1. Space gets eaten up very quickly if you have media assets. I've had clients with 30GB of media assets in a month. It once crashed a hosting company's file system it was so big.

2. People pay thousands. It is being used by some of the largest companies in the world and largest websites. Most people, of course, don't need to spend that though.

3. It's logging in a user, you have to hit the database to check credentials.

4. WordPress is powering 40% of websites out there right now? It makes sense.

5. I didn't dig further into it, but it was interesting to see those results