Cars are not the same as snakes. A Honda is a Honda, exactly the same Honda, even though there's new ones on the market.
A snake is bigger and therefor closer to being breed-ready after a year. You're not only selling the snake, you're charging extra because you're buying TIME. Time that you personally don't have to wait for the snake to grow.
With males it's not as predominant as females, but males can sell for more if they're "breeding size".