You seem like you know some stuff about how the body works, Canididizzle, but you are using the term BMR wrong!
BMR=Basic Metabolic Rate. This is how many calories a person burns every day just to stay alive! This means, if you were lying in bed not moving, your body would use the equivalent amount of calories as your BMR to just stay alive (breath, your heart beating, keeping your organs working etc). BMR does NOT include your daily activity. As soon as you move you will need energy for this and your daily calorie expenditure increases.
This is the BMR formula:
Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
When you say in your example 3000cals in one day you are speaking about the total amount of calories your body burns in one day INCLUDING daily activity.
A 30 year old male male that is 5'10, weighing 220lbs has a BMR of just bove 2000cal just laying in bed all day. For a BMR of 3000cals at 5'10 you would need to weigh above 350lbs.