From what I've seen at my recent replite expo, adult pastels go for around $140, with the highest one that I saw at $180. Since 263g is fairly young, I'd go no higher than $130-140.
I thought OP was talking about female pastels. Thats the price with males.
Females that are older cost much more; in the $400 to $1,000 depending on quality.
[6.18 Ball Pythons ]
Clown, Champagne, Pied, Pastel Lesser, Enchi, Fire
Albino, Bumble Bee, Pewter, Black Pastel, Lesser, Pastel Het Pied, 2 Mojaves, 2 Pastels Het OG, 2 Spiders, 3 Het Pieds, 3 Normals