Elon Musk said this weak that cheaper Teslas are on the way. But how many buyers will want one?Lisa O'Connor/AFP/Getty ImagesTesla reported disappointing results for the first quarter.But investors celebrated news of cheaper vehicles on the horizon.That assumes lots of people want to buy a Tesla but can't afford one.Tesla had some bad news and some good news when it released first-quarter earnings.The bad: It reported revenue and earnings that w…