Ultracycling

Including bike?

http://felixwong.com/2015/07/how-much-does-it-cost-to-do-the-trans-am-bike-race/

$3000-4000 depending on how you cut it. Other people will be more/less expensive depending on their airline tickets, how often they bivvy vs. hotel, how fast they ride it - faster riders might have more expensive kit but they will be riding/eating for fewer days and possibly using fewer hotel stops. Short answer: no idea, but probably pretty expensive for me.