Before I became a designer, I worked as a manager at various sneaker stores. Here’s a sales trick I learned that worked nearly every time: When a customer came in looking for a specific style of sneaker, I’d bring out what they’d asked for and I’d also bring out a less expensive but comparable pair. I’d tell them the other pair was just as good but was $10 cheaper. (Only when it was true, of course; I never lied about this just to make a sale.) Even though I made commission on every...