Adrien, you hit just the right spot! I don’t know how many times I’ve been in situations you’ve described. I often ask the person I’m conversing with if he/she values his/her time. You can guess that they always answer with affirmative “yes”. Then I subtly follow up with why don’t they value my time. Trick is in knowing how to handle people and not be cheeky (or worse) about it. An absolute read on this matter that I suggest to everyone is Dale Carnegie’s How to Win Friends and Influence People.