Oracle is worth every penny that they charge. Unless you've worked with it, you won't understand the love / hate relationship toward it.
Yes. It costs money. Why? Because it does so many things that nothing else comes close to. Its query optimizer is insane. MySQL is a toy and PostgreSQL, while admirable, remains in a lower class.
I say this as a supporter and contributor to open source databases. Like the open source cars of tomorrow; you can't compare them to the pedigree of a Porsche.
I was always a Sybase and DB/2 guy myself, but Oracle could do things. Things Sybase couldn't be tuned for. You don't put Wordpress on Oracle. You do crazy insane shit on it that will break MySQL.