Comment by logifail

> an internal financial model

Written on the back an envelope?

Way back when, we ran a vending machine at school as a project. Decide on the margin, buy in stock from the cash-and-carry, fill the machine, watch the money roll in.

Then we were robbed - twice! - the second time ended our project, the machine was too wrecked to be worthwhile repairing. The thieves got away with quite a lot of crisps and chocolate, and not a whole lot of cash (and what they did get was in small denomination coins), we made sure the machine was emptied daily...