Over the last year or so I've acquired 100 shares of Tesla. My average basis is $217.
I acquire stocks like this as "flyers" more than investments. Over the years I've done well with speculative stocks like this, with gains in Netflix, Amazon, Google, eBay, Facebook and the like. Most of my portfolio is in more conservative investments, but all of my big gains have been from "flyers", far exceeding losses in similar stocks.
As an aside, I think terms like "overvalued" and "undervalued" have no meaning except in retrospect. In a free market and without manipulation or inside information, a stock is always fairly valued, in that a roughly equal number of buyers and sellers exist at any price point. As I write this, Tesla is worth exactly $301.25, no more, no less. It is, at this moment, exactly as likely to go up as to go down.
If a year from now, Tesla is at $800, we can all agree it was an undervalued bargain at $301.25. If it goes down the tubes, we can all talk about how obviously overpriced it was at $301.25. The key is this only makes sense in retrospect.
My opinion is formed by decades of hearing talking heads pontificate about stock values. For instance, go back in time and you can find those saying Apple was overpriced at $20. It's now at $145, and that's with multiple splits of 2 for 1 and one at 7 for 1.
I recommend Taleb's "Fooled By Randomness", which I think informs my opinion as well.