Although I'm sure there is some truth to your comments, it really is not that simple. Firstly, the days of a supplier swaying a decision through sweetners is pretty much over. I can't say it doesn't still happen but it doesn't happen as much as you might thing. If you look at the database engine alone, then there are some valid and reasonable alternatives to Oracle - IBM DB2, Sybase SQL Server, MS SQL Server, PostgresSQL. Superficially they provide similar functionality. Large organisations quite often use more than one of them. However, anyone who knows much about databases know how substantially different they are. Oracle for example has it's own flavour of the SQL language as well as PL/SQL. Worth mentioning that you can also execute JAVA inside the database as well should you want to. Each of the DBs will have some alternative and it's not so easy to move that code between engines. Clustering is a good way to see the differences between the products. Oracle has something called RAC which attempts (sometimes pretty well) to make a database simultaneously available on several (potentially many) hosts at the same time. DB2 also supports clustering but does so by partitioning the data between different nodes. MS SQL Server supports basic failover clustering. I can't comment on Postgress or Sybase but it's clear that everyone has their own way of doing things. Another area where Oracle differentiates itself is through a number of other features - ASM for storage management, Oracle Application Server for application development and deployment. After all that, there is also products like Exadata.
I'm not suggesting for a moment that Oracle is superior (although it's the DB I know the best), but there are numerous substantial differences that dictate the decision an organisation makes, beyond cost or golf outings. More importantly, you'll find that the reason why a company will stay with a product is because of their investment in that product. It's not easy to lift and drop an application from Oracle into Postgress if you've taken advantage of the features. Making the move from one product to another could take a large organisation a decade to achieve and still find itself with pockets using the 'old' product.
Anyone can make an omelet with eggs. The trick is to make one with none.