Thoroughbred racing is referred to as “the sport of Kings”, because historically it was a leisure activity of the upper-class. Thoroughbred breeding on the other hand has transformed from a hobby of the upper-class to a worldwide agricultural industry. With the deep involvement of the royal and rich in the Thoroughbred industry, the auction prices of horses are raised significantly at the top end of the market. Research in the biological sciences suggests there exits correlations between dam age, foal birthrank, and the racing performance of Thoroughbred horses. This study first investigates how the market values these biological factors and whether they are correlated with racehorses’ career earnings. We further test the impact of sire age as there is limited literature related to the subject. By using a Hedonic pricing model, results show that Thoroughbred buyers at Keeneland September Sale are willing to pay more for the yearlings at 1st, 2nd, and 3rd birthranks, yearlings out of younger mares age from 4 to 10, and yearlings by experienced sires age from 12 to 18. Results from multivariate regressions suggest negative correlations between foal birthrank, parent age and career earnings.