Like g.ordon says i think selecting a mark suitable for the conditions and time when the match is to be fished is half the skill...
In regards to prizes i think the top prize always has to be big jusf to draw a crowd.... People are less likely to stake 10 to win 300 than they are to win a grand
It's difficult to select a mark when the boundaries are so large its not as if you can move 20 miles halfway through a match or if conditions aren't quite as expected. Trouble is that too many marks can fish when boundaries are so big. It a big sea is running it becomes much easier but its mostly flat nowadays turning the matches in to somewhat of a lottery!
I would happily pay £20 to fish if it was all paid out and wasnt spent on kettles, toasters, rod bags or Grey's fleeces. 20 good prizes is all that's needed. Often prizes are not even worth the entry fee let alone the full days fishing costs! It's an insult to wait around for a rig wallet!