This question always means nothing to me. If I get on a roof, it is stocked and papered and a 5 pitch clear run gable, sure I'll put up 20 square in a day. But this is rarely the case.
Steeper = slower
Fighting siding to get new flashing in = slower
penetrations = slower
valleys = slower
ridge vent = slower (hand driven)
cut up (A frames, dormers) = slower
100+ degrees outside = slower
wet wrinkly felt = slower
If I can put up 4 or 5 square a day on a steep cut up roof, and I know the chit won't leak til the shingles fail, I'm happy with that and I can make money.