Given that they can't imagine even the pain that they have, I have started asking it differently. I now tell them that 10 means "you need to go to the emergency room right now." Since most people are nowhere near needing the emergency room, this slows them down and I get more realistic answers most of the time. Yet, some people insist on telling me that their current pain is 10. I have a very hard time believing them when they are sitting fairly comfortably in the chair in front of me.
And there are some people that still think that they need to impress on me the immediacy and magnitude of their pain, and they insist on telling me that their pain is "12/10". So far, I have managed to resist the urge to slam down my chart, roll my eyes, and sarcastically excuse myself to go call the ambulance for them. All they end up impressing on me is their fantastically low pain tolerance.
If you want me to take you seriously, give me a 6-7/10 and I might believe you. Especially if I can start to see it in your eyes. That's a lot of pain. In order to be a credible 8-9/10, you probably are not able to sit comfortably in your chair or walk in normally. And some people legitimately are a 10/10, and I have sent a person or two from my clinic to the hospital, though we don't typically have to call the ambulance. So if you really need to go to the hospital I want to hear it.
By the way, I hope you never have to see the inside of an ambulance. But if you do, you need to remember the pain scale changes. Then 10 is the worst pain that you can imagine, and you better kick the imagination into gear. If you complain of 7/10 pain and you are not writhing and pale, they will roll their eyes while they strap you down and take you in. Luckily, I don't have first hand experience of this. But an EMT and I did get into a discussion on this once, and he didn't have any more tolerance for it than I do.