The PM has a point, at $1500 a cabinet minister is hardly going to sellout  for such a small amount of money. The problem is that by holding such events, you create the perception among many that they have. Obviously there are some people who are never going to be convinced that politicians aren't selling out to corporate interest, but there are many that are not sure. It is the group that are suspicious that you have to worry about, and even though common sense suggests that the amount charged is too small, by having these vents you create a potentially negative image.