It's crazy, there's a par 3 course here in Calgary, and it's 9 holes. It costs you $13 to play it, and it you want to play it twice - the second round is $7. So it's $20 for 18 holes.
It's a fun little course, but I didn't realize that playing it so much had helped my short game immensely. When I went out and played at a "real" course, the short part of my game had gone from one of the worst parts of my game, to one of/if not THE best.