You can just throw money at Postgres problems and make them go away. There are a number of very capable firms that do nothing but Postgresql support. And, they don't hold you captive w/ licensing. And if your needs are really that unique they can help you with building extensions to postgresql that support the capabilities you need.
See http://www.commandprompt.com/support/ for an example, or http://pgexperts.com/services.html
Why not? The free versions exceed postgresql. If you succeed and face heavy load, then you just throw some money at the problem rather than blow hundreds of man-hours fidling with the hacks people use to scale the free DBMSes.