Honestly, I cannot believe this is even a conversation?
$500 for a proven Enchi female is more than fair. I cannot see the pics, but if you like her look that is a great deal.
She has eaten a few hundred dollars in rats to get that size, not to mention time and other resources. She is likely at least 2 years old, meaning she was bough for at least $400 as a hatchling. Also, Enchi females are worth their weight in gold. there is a reason you do not see a ton on the market!
Anyone selling an Enchi gal of that size for less is selling themselves short, and screwing fellow breeders to boot!