It depends, and unless you really know the history of the camera, you really just cannot tell.
I certainly know I would never buy one of my boss' 5Ds, the way she sprays and prays in her shoots. I have a 10D (now a seven-year-old camera) that has under 20K shots on it, and is cosmetically trashed. This camera did see regular, though not heavy, professional use (probably 5 events a week on average, when I was actually working steadily) for the first five years of its life, when I shot for a newspaper and lots of bands. I would call it "semi-pro" use. Even then, it only has that many shots on it. I only use it occasionally now. The shutter is still perfectly accurate and everything works as it did when new. I have had it serviced once, at five years of age, to CLA it, and fix a loose shutter button, and have had the sensor cleaned at least 20 times. I used to have this done free, by Canon. She, on the other hand, will shoot at least 2,000 shots on every full-day job, so her shutters have to have been fired well over their specified shutter life by now, and I know she never has the cameras serviced, and never will unless they break. On the other hand, her cameras look cosmetically pristine, and seem to work just fine. Go figure!
If I was a third party, and knew what I knew about both my and my boss' cameras, I would buy them from neither of us...but if I did not know about them, I would probably buy hers because they look better taken care of...and have my shutter start acting up after those hundreds of thousands of exposures.
So, you just never know...unless you happen to know!