This week's book giveaway is in the Other Open Source APIs forum. We're giving away four copies of Storm Applied and have Sean Allen, Peter Pathirana & Matthew Jankowski on-line! See this thread for details.
Oh yeah, it's a LOT more expensive. You should use it only if its a major project that is mission-critical for the business. Otherwise, consider using other DBMSes such as mySQL which is I think 3 times faster than Oracle.