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The Postgres faithful rejoiced last week when Amazon(s amzn) CTO Werner Vogels announced that Amazon’s Relational Database Service (RDS) now supports that open-source database. But some of the bloom came off the rose when they realized that Amazon Web Services is charging more for Postgres than it is for MySQL.

That’s particularly galling to this group because, while MySQL is also an open source database, it is owned by Oracle(s orcl) and that typically means higher support and maintenance fees. So how is it that yet MySQL is cheaper than Postgres (aka PostgreSQL)?

One Postgres user, who requested anonymity, is perplexed by this, because the knock on MySQL is it’s an Oracle product and thus is seen as more expensive in terms of support and service than Postgres.

His company runs Postgres now on-premises and would be happy to offload it to RDS, but will not do so in light of this pricing. “We find it strange that Amazon RDS has chosen to price MySQL 5% to 15% lower than PostgreSQL,” he said via email. “Both PostgreSQL and MySQL are open source — meaning free to Amazon and the developers [but] if you look at Amazon’s pricing table and compare instance-by-instance and Multi-AZ prices, you will see PostgreSQL prices are 5% higher for Single AZ and 15% higher for Multi-AZ.”

“What is even more crazy is that Oracle’s (bring your own license) model is priced the same as MySQL (meaning 5% less than PostgreSQL),” he said. (See price comparison charts for single- and multi-availability zone Postgres vs. MySQL pricing below.)

An AWS spokeswoman said “RDS pricing varies for each database flavor because our costs vary. These costs include many operational components beyond software licensing.”