Why do perfect run scores in the same stage vary so much?

I'm sitting with a pen n paper, trying to compute the theoretical maximum score in Stage 1! Why do the base scores vary by up to 3k even on perfect runs?
Till now I have found the wooden crates giving 1000 points/stars/power-ups as the only possible variation. Is there more?
Best Answer
There is some variation in what powerups are dropped from glowing planes and that are found in crates.
If you are full health, then health hearts give you a small amount of points, but these seem to drop randomly with main weapon power ups.
Pictures about "Why do perfect run scores in the same stage vary so much?"



How to Deceive Defenders? Clever/Intelligent Runs
More answers regarding why do perfect run scores in the same stage vary so much?
Answer 2
There is a huge points difference in how fast you beat the boss at the end. Don't forget about that!
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Trần Long, Pixabay, Alena Darmel, Alena Darmel