Very interesting! I like the art style and the concept of the game. If the weight checking was a little bit convenient it would be better, i had a hard time putting items right on the scale XD. I think you place a trigger box up above the scale to check what objects entered the scale's range, and if those objects is not held by the player and the velocity is 0, we can basically tell that they are on the scale.
Overall I think that this tackles the jam's theme really well and quite creative! Good work!