If you have a level 62 (or lower) item from a lvl 63 monster, each affix appears to have about a 10% chance of rolling at the top range.
So your chance to get all 6 affixes in the top range would be 10%6 or 0.0001%
Of course, the 0.0083% chance you have on a 6-affix lvl 63 item (45%6) might not look too attractive either, but this is 83 times more likely to find 6 affixes that are all at the top range.
In other words if your first priority was to toss anything that didn't have all 6 affixes at max range, and someone gave you a choice between 13 unidentified ilvl 63s or 1000 unidentified lvl 62s, you're more likely to find what you want in the small pile of ilvl 63s.