Companies have been pulling this shit in the uk for years and years before brexit. It's just now they can rip people off and use it as a handy scapegoat while crying that they don't want to but they have to.
wagon wheels, lion bars, monster munch, malteasters, mars bars, creme eggs have all shrunk in size compared to how they used to originally be.
Let them keep going, they will eventually see what happens when people stop buying and their profits nosedive.