On the topic of Favors (running a game for free), or “Barter” (small non-cash rewards) or direct payment - there is a book that is perfect for understanding the confusion around these patterns…
In Chapter 4, Dan Ariely recounts an experiment where people were asked to do a mundane task (drag circles into targets on a computer):
"[we asked some to do the task without any reward, others] we offered a Snickers bar (worth about 50 cents), and [others] a box of Godiva chocolates (worth about five dollars).
The participants came to the lab, got their reward, worked as much as they liked, and left.
Then we looked at the results.
As it turned out, all three experimental groups worked about equally hard during the task, regardless of whether they got a small Snickers bar (these participants dragged on average 162 circles), the Godiva chocolates (these participants dragged on average 169 circles), or nothing at all (these participants dragged on average 168 circles).
The conclusion: no one is offended by a small gift, because even small gifts keep us in the social exchange world and away from market norms."
So far, so good, but here’s the surprise:
"…[if] we labeled them as a “50-cent Snickers bar” or a “fivedollar box of Godiva chocolates,” what would the participants do?
Would a “50-cent Snickers bar” make our participants work as hard as a “Snickers bar” made them work; or would it make them work halfheartedly, as the 50-cents [cash] made them work [in a previous experiment]?
As it turned out, the participants were not motivated to work at all when they got the 50-cent Snickers bar, and in fact the effort they invested was the same as when they got a payment of 50 cents [Much lower!]
They reacted to the explicitly priced gift in exactly the way they reacted to cash (also lower), and the gift no longer invoked social norms—by the mention of its cost, the gift had passed into the realm of market norms."
This reflects the attitudes of people who feel “icky” when talking about Cash for DMing (which they think of as a social-market activity) but have no problems with unpriced-food/drinks as compensation. Think about what would happen if the player that brought the food bragged how much it cost…
If someone puts a cash price on an activity I’d do for free, it feels like my volunteer effort is devalued, or that I’m some kinda fool for “giving my time away.”
The truth is, there is no hard and fast rule here. If you want to share your skills as a DM with your friends, go nuts and have fun. If you can’t find a game and are willing to pay $ to get a game running, have at it!
As always, expectation management is everything.
There are so many border cases, it isn’t funny.
For example, I run a game at my local FLGS.
They “charge” 5 dollars for the session to each player. For that $5 they get a gift certificate good for $5 at the store, redeemable immediately (or they can be collected.) I get 20% discount on everything I buy at the store.
No one gets paid, or everyone is getting paid, depending on when you do the accounting. But no one is getting rich, and we’re all having fun.