Contrary to conventional wisdom, goats really don’t eat just any old thing. And what they’re eating this summer is profits, to a point that the goat milk supply and some farms are threatened.The largest goat milk buyer and goat cheese maker in the country ? Montchevre, based in Belmont since 1989 ? this week upped by some 3 percent the price it pays for raw goat milk from its 350 suppliers in an effort to preserve its milk stream. Thomas Cox, a UW-Madison agriculture economist, said the increase is a necessary response to the drought that will probably be copied by the dairy industry as feed cost increases ripple through agriculture.