Here’s the thing, I firmly believe that Dwight has an extreme amount of money and is quite possibly the richest guy in the office. Obviously he has the income of the best salesman at Dunder Mifflin paper company inc, but he also has the income of his beet farm which has the best beets in the state, but additionally he uses his home as an air B&B. Even with those all as sources of income you could imagine that he would be extravagant in some ways (weapons). But seeing as he also uses beets as a main source of food he saves on groceries and he also doesn’t splurge on many things such as additional clothing or going out. Also seeing that Dwight has an abrasive and micromanaging personality it’s easy to imagine that he keeps a tight budget and sticks to it. With all of these facts it’s easy to see that Dwight could easily have a surplus as opposed to a deficit and by saving this (which he would) Dwight would have the most money out of everyone in the office.