I see your point, but I strongly disagree. Providing a suicidal person with the right resources to help them avoid suicide will (imo) yield a net gain over the rest of that persons life, as opposed to the gain from selling a gun and a bullet and giving him a quick out.
One example that comes to might right away is Alan Turing. Whose contributions to modern society can hardly be overstated. And I know he didn't use a gun, I'm making a point about helping people out of depression, to oppose your opinion about it being beneficial to let them kill themselves.