Being closed source and a paid application oracle hurts your bottomline more than once. Not only do you spend money buying the expensive license+machine but you end up paying more for maintenance and administration.
Lets compare the cost of a MySQL/Postgres database to an Oracle.
|DBA cost||High ($30K/year)||Medium ($20K/year)|
|License cost||High ($600K + $100K/year ~ approx)||Nil ($0k)|
|Downtime cost||High (Revenue)||High Revenue)|
And after all this money spent when it crashes it hurts much more as the cost of the downtime is the same i.e. loss of revenue. It you much more as it has already eaten into your revenue. Speed wise there is hardly anything that can match MySQL. However it is not as reliable as Oracle/Postgres. But then if I maintain say a 3 node cluster of MySQL it is much more reliable and cost effective than Oracle.
Oracle has always been touted as the most feature rich database. However I don't think most of the websites out there use any of those advanced features.