Does Apple need more smartphone market share?

I've heard and read multiple times how Apple needs to release a low–cost iPhone. If they don't do it they're doomed. Or so they say.

You see, they talk about a budget iPhone as if it was some sort of life or death situation. Apple plays the profit margin game, not the sales volume one. Is Apple supposed to lower its profit margins even more just to increase revenue?

Why should Apple enter the low–end phone market and not the low–end laptop market? In 2013 the most economical Apple laptop costs $999. Apple clearly can't compete against those sub $400 laptops, and thus must be doomed.