Tesla is waving goodbye to the Model S and X with an exclusive, limited-edition run of its pioneering EVs. Elon Musk's automaker is inviting a select group of fans to purchase a "Signature" variant of the soon-to-be-discontinued luxury models, according to screenshots and videos circulating on social media. The "Signature" Model S and X both start from $159,420 — a nod to Musk's favorite number and around $60,000 more than the original models — and come with free supercharging and Full Self-