Well I'm going to be the odd one out, but I don't think a scale is that important. I have one, and only use it for measuring females during breeding season. And even then, I don't use it that much. I use it more as a "I'm pretty sure she's gaining weight back, I'll double check with my scale" sort of thing.
For feeding, there's really no need for one to be honest. Just feed your snake something that is 1.5x's wider than the largest part of its body. Feed that size until you can no longer see a lump and move up in prey size. Keep doing this and then stop once you hit jumbo mice. Even if I can't see a lump, jumbo mice are as big of an item as the get. This is so much easier than messing around with weights and works great. For feeding frequency and what not, by all means turn to the Munson Plan.
But obsessing over prey weights vs. your snakes' weight is pretty pointless IMO.
Now that being said, owning a scale isn't a bad thing and I'm glad I have mine. But for just feeding, its not needed.