If you are just starting out and are focusing on web development, I'd recommend JavaScript since all you need to get going is a browser and a text editor.
Is it sane to ditch JS (and node.js, angular.js, bootstrap.js, ...) and go with clojure? (maybe even ruby?)
Clojure/clojurescript will get you a single language on front-end and back-end, but I think that from a monetization standpoint you really want a Javascript front-end and Java or Ruby back-end.
Keep in mind that if you use "more standard" technologies, you'll also have a more likely chance of cashing out on whatever you build if you decide to sell because the buyer will be able to hire people to fix it. If you choose something obscure without a developed community, any price offered to you will be much, much lower or even just never come.
I'd personally skip the node.js hype for now.
On one hand, I like using something that makes me think and also gets the job done (clojure). On the other hand, it feels good to be a member of a huge community (JS, ruby, python developers) and know what many others know.
I had not thought about your points about selling a software in a "less standard" lang. I think you're right.
Guess how that great performance comes about - C++ and non-blocking I/O! There's also the aspect of the community that makes packages for single functions and can't develop a useable package manager (last time I checked). I'm not against it as pure infrastructure for running clojurescript, though =P.