The bit about building a web app in C is totally off-topic from your claim that 100 lines of python would equal 100 hrs of Java. If you can only write good software in a short amount of time in one or two languages, that's just a reflection of you as a developer and not the language, and I'd seriously challenge you to show me something you've written in 100 lines of python that I couldn't hire a single senior Java developer to write in the same amount of time (lines of code doesn't equal cost, so I'm not interested in debating lines of code nor do I think it's a valid measure of anything).

I'll give you a short story that approaches this issue from both sides. A client walks into a consulting shop with a piece of really bad client/server software written by a different consulting shop. The server is written in Ruby/Rails and the client in Java (Android). Both client and server code is horrible even though the server is written in Ruby (a supposedly beautiful/compact/expressive language) and the client in Java (super ugly long winded grandpa language, or whatever). The client paid the original consultants about $60k in total. One Ruby engineer and one Java engineer rewrote the entire thing in a few days for 1/20 the cost without really reusing an ounce of the original code. Ruby didn't stop the original server engineer from delivering horseshit in too much time, and Java didn't stop the second client engineer from delivering a clean/functional/performant app in just a few days.

Your second paragraph is what I meant

But I've never seen a "software consultancy company" do a project except in Java

Ruby and Python can be beautiful yes, but in the hands of average Java programmers it just becomes a horrid mess