“It was totally worth it.” In this case, “it” referred to a Vitamix blender that a friend recently had purchased. He wasn’t the first. Indeed, I don’t know anyone who has purchased a Vitamix blender and didn’t share my friend’s effusive sentiment, even after spending between $429 and $719 (for the new line of G-Series models). For a blender.

But despite my appreciation for these friends and their opinions, I can’t help but notice their errors in judgment, explained by behavioral science, that, if followed, could lead to an unwise purchase for you or me.

To be clear, it’s not their purchase of the blender that I’m questioning. Rather, it’s their insistence that said purchase is a universal must. Worth, you see, is relative. What is “worth it” for you may not be “worth it” for me. Ultimately, determining the worthiness of your next purchase depends on many factors, but chief among them are 1) the joy you receive from using the product, 2) your personal cash flow, 3) how much you will use the product, and 4) the cost of available alternatives.