Why did Borland fail?

I'm not saying there isn't any, and certainly I've used better refactoring tools than https://github.com/clojure-emacs/clj-refactor.el in other languages. But what on earth is wrong with the navigation? The main advantage I've seen form a colleague is the highlighting automatically of usages, but I'm pretty sure I can set that up in Emacs too.

A commercial new license is $500.

Not sure where you get the big price drop from ;) And yes, it is easily worth $500.

To answer this specific question - Cursive's Java interop support is much better than anything else I'm aware of. It implements Clojure's type inference in the editor, so method calls are accurately resolved to the right method based on the number and types of the parameters, and completion takes this into account so that you can explore Java APIs almost as well as with Java in IntelliJ. Cross-language navigation and Find Usages works - in Cursive you can navigate from RT.var() calls to the Clojure code, and Find Usages from Clojure will find the RT.var() calls. This also works for other JVM languages - there are quite a few Cursive users with mixed Clojure/Scala codebases, and this all works there.

You can search for all usages of a particular keyword, and it will also find all local bindings destructured from it using :keys. Namespaces will be auto-required during completion based on examples elsewhere in your project, not hard-coded config. This works in the REPL too - you can type str/tr and when it's completed into str/trim Cursive will automatically (require '[clojure.string :as str]) in your REPL.

One other nice thing is that since Cursive works from source, pretty much everything that works for Clojure works for CLJS too.

There's lots more along the same lines, hopefully this gives you an idea. Again, there's nothing wrong per se with Emacs' navigation, but IntelliJ just provides a much more sophisticated infrastructure for it. Obviously elisp is Turing-complete so all this could in theory be implemented but it's much harder, as Yegge describes in the article I linked in my other comment. The clj-refactor guys are doing a great job but the lack of a good indexing infrastructure is going to mean that a lot of this functionality is hard or impossible to implement.

Emacs is a great choice for a lot of people and if you're willing to invest the time to trick it out and maintain it, especially for Clojure you can get a really nice environment. But probably the feature that most people like about Cursive is that it just works out of the box, and stays working with no messing around and no development of your editor required. And WRT my original comment - to say that Emacs has the most sophisticated runtime analysis is just wrong.

It goes on and on. When I considered it for a project the cost came out to almost $5000! Instead we went full open source (including JetBrains' open source version of PyCharm) and got lots of functionality one couldn't find at any price on the Delphi platform - which incidentally is, just now in 2015, beginning to set up package management. Unfortunately it will be tightly controlled by Embarcadero and they've issued all sorts of warnings about not approving code that replaces functionality in Delphi (in short, they're afraid of competition). The community has no control over the language or the product and the diehards that are left treat it like a religion. They have something called "MVPs" who actually sign a contract to never disparage the language or Embarcdero! In exchange for selling their integrity they get free copies of the product. Completely coincidentally, they'll tell you that the product isn't overpriced. They'll also tell you it's used all over but no one talks about it because "it's their secret weapon". Delphi's product manager told me that he fully believes that "Delphi has had a greater impact on the business world than Python ever has". You not only have to pay all that money, you have to deal with the Scientology of programming languages. :-(

So no, you pay far more than for IntelliJ, you have no control over the product, you have no working roadmap, you don't even have RELEASE DATES for new versions. It's a whole other world over there than what the rest of us are used to.