Complex sentence: This race is restricted to two-year-olds who have been sold at auction, with the basic weights being set by the sale price and as Superstar Leo had been a relatively cheap yearling, the race was an obvious target.
Split into simpler sentences: This race is restricted to two-year-olds who have been sold at auction, with the basic weights being set by the sale price. As Superstar Leo had been a relatively cheap yearling, the race was an obvious target.