Just reading an article about how the inaugural NYC Ironman triathalon (not to be confused with a non-Ironman triathalon) might be the world's most expensive with possible entry fees of $750 - $1,000 per competitor.
The parent company doesn't believe they will have any trouble with people fronting the fee however as:
"The cost may not deter competitors.
About 2,000 of the approximate 3,000 competitors in the 2010 NYC Triathlon worked in the financial services industry, race officials said, and
Ironman competitors have an average annual income of $161,000, according to World Triathlon."
From:
http://noir.bloomberg.com/apps/news?pid=20601079&sid=a709xnIhIYyMNever thought of a triathalon as being in the same category as polo (Yes, sweeping generality, I know).