"Fun" is perhaps entirely a subjective phenomena: our perception of it is certainly highly subjective, and it is difficult to point to an objective standard that our perception reflects. One who acquires sufficient self-control can have "fun" doing anything (even profitable things!). Because of the ease with which we can bend our perception of fun, and the difficulty in keeping this feeling aligned with anything outside ourselves, "fun" is generally a terrible star by which to steer. Those who attempt it often seem to end up chasing their tails: and I have fun watching them.

"Profit", on the other hand, is an objective standard, so it is possible to keep our perceptions of it aligned with reality. It is not quite as easy as, say, temperature: where we can stay calibrated by hauling a simple instrument around. It is often more difficult to predict the outcome of a particular transaction: building up the fire is a reliable way to increase the temperature in our house, but investing our resources so as to reliably make a profit is more difficult. There is a lot of random noise to obscure the issue: "I won the lottery! See, lottery tickets were a great investment after all!". The timescale upon which profit operates can be longer than we can perceive. To further confuse the issue, humans have dual natures, and what can profit one side will often cause a loss for the other: necessitating some hard choices at times. Still, despite these difficulties, over the long haul "profit" is a star that will guide us consistently if we mind it.

Of course, a person can always chose to ignore the objective nature of profit, and warp their perception of "profit" in any way they please. If they blow their day playing in the sun, they can tell themselves that really this was quite profitable in some way perceptible only to them. They might even convince themselves that their naval lint was as valuable as gold, and start hoarding it in jars.

I'm not sure that warping our perceptions is really a wise thing to do: but it seems a lot safer to convince oneself that what is profitable is fun, than the other way around.

As a final note: the fact that we can quote people we have never met, like Jones; and people long dead, like Thoreau: suggests strongly that they were guided by the star of profit.