It also depends. If you have friends living in other cities (preferably abroad) and want to make them suuuper happy, you could perhaps just fly and visit them for a lunch or something along those lines. They'll think you've lost your mind if you're coming only to have lunch with them, but you'll probably get your gold card.

PS the cost of one segment might depend on the place where you are based. It can very easily become considerably more expensive if you live in a city where Air France has got less competition, like, say, anything in France that is not Paris/Lyon/Marseille/Toulouse. Even flights to and from Bordeaux are considerably more expensive, and that applies also to flights operated by KLM.