Can you explain why you are so against purchasing a scale?
I use mine all the time, it is an extremely useful tool for keeping healthy snakes, and at $15 it was one of the cheapest tools in my arsenal.
a scale can:
1. help you track the development of your snake
2. allow you to feed your snake the correct amount of food (15% of the snakes body weight)
3. allows you to track weight loss when a snake stops eating (this allows you to determine when it is time to take more drastic measures)
4. Allows you to easily track the development of females when breeding (I under stand that not everyone who has a BP plans on breeding)
I use my scale on all of my snakes at least once a week. considering I spend $15 on it, and I have used it hundreds if not thousands of times already I certainly think that it is well worth the price.