Hm... One could argue that there are 3 separate dials, each with the digits 0-9, and you don't know whether you've gotten one right until you've gotten all three right
So then you get 10*10*10 = 1000 combinations, which happens to be the same as counting from 000-999. The fundamental difference is in the number system used. Don't confuse this type of lock with a single-digit lock simply because it appears to behave the same way due to the base-10 number system employed. Let's imagine that the same lock had the numbers 0-9 and a-z on each of the three dials as well. Now there would be a number system of base 36. To someone from a planet where the natives had 18 fingers on each hand, they could argue it is simply a "one-number lock", despite three separate dials of 36 possibilities. Notably, the total number counted to would be 36*36*36.
Factorial calculations only come in when a number can NOT be repeated. On most types of locks, numbers can be repeated, so you never get into factorial calculations. I'm sure you know this, but your post made it seem a little murky, so I thought I'd clear it up in case other people are reading. For an example, on the common 5-digit mechanical locks often found in US dorms or hotels, the numbers can not be repeated. (these are the locks with 5 buttons, usually vertically aligned above the knob, and accept combinations such as 5-1-3-2-4). On these locks, the mechanical system mandates that the proper sequence be entered in the proper order, but cannot handle double-presses. Once a button has been pressed, it is out of the loop. So then you have 5! combinations to try. The first digit could be any of 5 numbers, the 2nd digit any of the remaining 4, the 3rd any of the remaining 3, etc. So you can compute the possibility as 5*4*3*2*1 = 120 combinations. On an electronic keypad that could handle repeated digits, it would be 5*5*5*5*5=3125 combinations. Quite a bit different here.
Perhaps the overall differences I've mentioned (particularly the number system ones) are trivial in practice, but don't discount them as insignificant by any means.
I guess I could just go make breakfast for my wife. 
