Bear in mind that quite a bit of Tesla profits are going into the Gigafactory, which is going to make them the largest producer of batteries in the world. So the cost for batteries for them go WAY down, and they can sell batteries to other companies for a profit. This is a big part of their plan. Their cars get cheaper to manufacture if they don't have to buy their batteries from third parties at a premium because they are sucking up a HUGE part of the market. If I want 70% of the batteries in the world, and others want those batteries, the battery manufacturer is going to charge me a premium for eating such a huge chunk of their capacity. ... and even more if they know I am using my profits to eventually compete with them. Also, if I am a battery manufacturer I want to please LOTS of customers, so while I like the idea of selling lots of batteries to one guy, it costs me customers. If I am a Lithium mine operator, I don't care. My customers are middle men. If I can sell everything I can mine to one guy and my life gets simpler. I don't care if it hurts some other middleman.
The Gigafactory is going to change the economy of scale for Tesla.