Most believe, myself included, weight loss and gain to be a good indicator of general health. This makes it a valuable addition. A scale does not need to be accurate as long as it repeats the same object to the same weight. This might not be true for selling snakes then I feel accuracy should be quite good.
I found a cheap scale that I check for both and was quite surprised by the result.
Starfrit slim glass kitchen scale
It is quite small only 1/2 inch tall and a glass top about 5.5x8 inches. It can read in grams or oz it fails as the max weight is 5000gm enough for many animals not all. I use a plastic tub to weigh in this scale zeros well and easily. The height is a great bonus as the tubs often slipped off my taller scale and you had to catch it. This one if they slip is just leans a bit the snake isn't jostled at all.
I use a lab grade glass graduated cylinder zeroed out. Added 150 mL of distilled water 500mL and 2500mL and weight these the results were 149 fluttering to 150 (no half gram I figure it is 149.5) 500gm and 2501gm. I removed each and repeated 3 times with each weight the repeated results were the same (the 150 stopped fluttering and stayed at 150 and 150 and 149.)
I then out of concern for the low end used a calibration weight 10gm and it was measured at 10gm and repeated this 4 times.
I bought this scale at Canadian Tire but it is carried by many other stores at least in my area. In my case (sale) I paid about 15$ for it. The regular (CT) price is 30$ ($28.39). I thought I'd share as I am quite pleased by this hidden gem.