It's an older saddle with no padded flaps. This style of saddle is not popular anymore. $500 is reasonable, but you'll have a hard time selling it because of the flap style.
You won't sell it well on eBay if you don't have a decent amount of recent feedback on an established account. New accounts with less than 5 feedbacks rarely sell things high. If you don't have an established account with good feedback, then have a friend try to sell it under their account.