SoundHound AI (SOUN 15.38%) is likely one of the cheapest artificial intelligence (AI) stocks available (at least on a dollar-per-share basis). While most brokerages offer fractional shares, not all do, and that can limit what stocks investors can buy.At around $20, SoundHound is a fairly affordable investment for most people, but the stock is far from cheap. How can a stock be affordable and expensive at the same time? It's all about valuation.SoundHound's stock has been on fire latelySoundHound AI is one ...