My recent (a few hours ago, in fact) entry into an online group where the business side of writing is discussed has put me into an accounting mood. So I have been playing and running some numbers to come up with my (or yours) expected return as a short story writer. That’s the key concept here since novelists or self-published authors will have to come up with their own numeromantic equations to see how much they need to sell to not be ashamed of saying that they are writers.
It’s really not a complicated thing to calculate since the short story market is relatively open and static about key economic data. If you know their payment and rejection rates, you can improvise the rest.