Take note Quigfen's store has all his merchandise with a positive modifier, this being Champion for this horse. The player does have to pay the extra cost of that modifier and then multiply that price by 2 to see his selling price. The horse without modifiers costs 19,002 denars, but Quigfen sells the Champion one for 551,058 denars (x14.5 for being champion and then his x2).
It should be noted that it is by far the fastest horse in the game, but it's pretty weak, and if the fall faints in a battle, its modifier may be changed to lame, and even though that can be healed, he will stand with no modifier (losing the champion status).
Champion Comet Courser requires 9 riding, and has an overwhelming 66 speed, 37 maneuver, 22 charge, 20 armor and 100 hp.