Caleb,
Most price their houses based on what they want to earn per hour (and then stick a little on
)
Your right you need to price each house on its own merits....going by pricing per window is ok, but doesn't take into account access issues, difficulty of the clean etc.
Pricing by working out the time it would take to clean the house gets easier as you get more experience. Some you will find will take longer than you had thought, some will be quicker.... so long as overall you find the middle ground then you won't go far wrong.
Again with bigger houses apply the same principle...one tip I would give you is if in doubt price the job based on the highest price you are thinking, as you don't want to underprice the job and then feel demotivated each time you have to clean it.
Cheers, Mike