I can understand why you would care about what language it is. But there's nothing wrong with charging more to work in a language you dislike; you just have to be upfront about that.
You care about the language SO MUCH that you would be willing to risk developing the app for free, or worse free + real damages + punitive damages (for fraud)?
There's no language that I love so much that I would risk a lawsuit over it.
Of course not. I totally agree that you need to have client approval over what you end up using. But my point is that if the client wants you to use a language that takes you longer, or that you are miserable to use, you can reflect that in your quote.
