It should also be pointed out that "cost of entry [including opportunity costs]" here can be smaller than the cost of time effort it takes to make art, if the contest involves any enjoyment, fun, or other benefits from just participating. In fact, the opportunity costs can even be negative. (Or alternatively, add a term to the inequality for other benefits.)
Even if not knowing the exact number of people that will enter, the reduced costs can let you estimate how many people it would take before it is not worth your time. It can easily require more entries than would be expected. Not to mention I've seen artists that increase number of prizes based on the number of entries, so the chances to win doesn't shrink if more people enter.
It should also be pointed out that "cost of entry [including opportunity costs]" here can be smaller than the cost of time effort it takes to make art, if the contest involves any enjoyment, fun, or other benefits from just participating. In fact, the opportunity costs can even be negative. (Or alternatively, add a term to the inequality for other benefits.)
Even if not knowing the exact number of people that will enter, the reduced costs can let you estimate how many people it would take before it is not worth your time. It can easily require more entries than would be expected. Not to mention I've seen artists that increase number of prizes based on the number of entries, so the chances to win doesn't shrink if more people enter.