I've developed 70 educational programs in Real Studio for use in the classroom. Many of these programs would not have been possible at all without the MBS plugins. Even though the plugins are amazingly comprehensive in adding core Cocoa and Carbon API access, the developer somehow has done a superhuman job of continuously adding even more functionality with each release. If you want to develop complex professional software with Real Studio, you must purchase these plugins.
By the way, before the typical troll on MacUpdate accuses me of being an amateur for using Real Studio, for 30 years I've developed neurophysiology research software in assembly, C++, LabVIEW, Prograph CPX and Java, to name a few programming languages, on laboratory minicomputers and several types of personal computers. I currently program in Objective-C as well.
I use the appropriate tool for the particular job, and for my educational software, Real Studio and the MBS plugins allowed me to quickly create professional applications that are used at colleges around the world.