After paying to run only a mile, I thought about the value or entertainment value of a race. Personally, I don't care how much a race costs. If I want to do it, I'm going to pony up the cash and not think twice about it...except for maybe the Tough Mudder. I've been going back and forth on this one because I'm afraid I'm going to hurt myself or get hurt by someone else.
Anyway, the Macklind Mile was $25 for a mile that took me 6:49 to run. The triathlon I did last weekend was $65 (due to a nice discount I got), the 5k the weekend before that was $30 but you got a medal and the Half-Ironman was $175 because I signed up really early.
So, for the Macklind mile that race cost me about $3.70 per minute, a very expensive race. Below are the cost per minute for the other races mentioned.
Octomax Tri: $0.67/minute (would have been $0.97 without the discount)
5k: $1.15/minute + medal (only mentioned because this is odd for a 5k)
Rev3 Knoxville Half: $0.39/minute
Average Ironman in 2012 if completed in 14 hours (excluding IMNY) would be $0.71/minute
So, it seems like two things are true. The longer the race the less it cost per minute until you step up to the Ironman distance (granted there are cheaper 140.6 races out there) and obviously the slower you are the less it costs per minute. Remember that if you're not winning races or your age group, you're just getting more bang for your buck and most importantly you're doing this because it's fun!