That alone would make it a hit. I don't believe thee are any current cars priced under 20k.
People haven't learned a few important lessons about Elon Musk:
Don't tell him that you can't build a rocket that can take off, and then come back and land itself right at your feet.
Don't tell him that you can't do a better job than NASA when it comes to putting things in orbit.
Don't tell him that you can't build a self-drive electric car.
Don't tell him that you can't build and sell an electric car for under 20k that can drive itself, has a battery that can exceed 40 years life expectancy, fully recharge in 10 minutes, and outperform most performance gasoline cars on the road today.