Talion is a fantastic card in the 99 of a Commander deck, or a Rhystic Study in the Command Zone
However, and this is very important, just as if you were running that race, and if you were attacked, you would probablyespecially if you felt that you could have wonyou would probably have said that you would have won the race if not for that nut-job who jumped out in the middle of it and hit you over the head with a sign, much as it happened to Isidor Lima in the 2004 Athens Olympics Men's Marathon event
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of Danitha Capashen's last ability)
and a Second Harvest reprint
If you can afford to cast it, and then keep six mana open until an opponents end step, activate it and exile something like ten artifacts from your deck to create ten 1/1 Myr tokens