Looking to get a price check on a cub I might be selling.

He's a Skyward base boy, only 6 months old with 300 stats on the dot. Not clean, has 1 instance of possible inbreeding. I had started customising him to use as my heir but my plans ended up changing, spent a fortune getting him quad cloudburst markings (slots 13-16 since the others were reserved for december apps), changing his mane shape, eyes, skin colour, etc.

I did a TC search and most are going for around 15GB but I'm wondering if other factors (notably the markings) add to his worth at all?