For example, clients who insist on using amateurs (sometimes themselves) to create a logo rather than hiring professionals?
I'm assuming the clients fall into the micro business or small business size? Because this is typical, mostly due to the fact they've little training on actually running their own business.
I usually relate to them using something of interest. For example, if I had a client who owned a cooking supplies store, I'd explain how a KitchenAid stand mixer costs twice as much, but lasts a lifetime. When they agree, we talk about the value of having spent more to have a product that looks great on the countertop, requires little maintenance, and ultimately costs less.
You have to talk on their level. It's not a lower level than yours, but a different one.