It's my opinion that the Trump team never imagined that Mexico would "pay for the wall." What's always been meant is "I will make those Mexicans pay for the wall. I will make them pay."
So, the plan is surely trade sanctions and more. The real point of the whole thing will never be cost recovery (nor true border security). It's ritualized combat display: the leader publicly acting out his supposed manly vigor and strength of will by exercising the organs of state symbolically to humiliate, impoverish, emasculate, feminize, and punish a straw-man external enemy erected for the purpose. He will try to supplant the reality of the Mexican people's complex humanity, society, and shared-with-us economy with a fictionally puny, dirty, criminal, and base caricature. He will ostentatiously pummel that piñata in order to give the masses of his supporters a vicarious victory and a sham sense of security, a warm spatter of fake enemy blood, while his regime, less watched, loots our inheritance and undermines our liberties, doubling down on the very sorts of injustices that underlie the rage against government and establishment that helped put him in office in the first place.