Holes by that cylinder- presumably in the wall or floor? The money goes into the locked treasure room, not the cylinder. And it causes (somehow) the cylinder to rise, not fall.

The idea is that the room in the dungeons has two compartments which the two holes lead to: one contains the locks and predictions, and only the 'winning' lock is used when the person is assassinated (my offline analogue to crypto signatures), but the other just holds the money/rewards, and is actually a big cup or something held up by the cord which goes up to the ceiling, around a pulley, and then down to the cylinder. Hence, the more weight (money) inside the cup, the higher the cylinder is hoisted.

I guess ropes and pulleys are no longer so common these days as to make the setup clear and not requiring further explanation?

(This is one of the vulnerabilities as described - what's to stop someone from dumping in some lead? As I said, real-world equivalents to crypto are hard. Probably this could be solved by bringing in another human weak point - eg. specifying that only the merchants are allowed to put money in.)