I would just suppose its individual snake differences. Prehaps different grades, like there can be two female pastels but one be 3-400$ more simply because of how her pattern has laid out.
Mostly I noticed the wavey sides to the back stripe, full or disconnected in places, and the brown circles that dot the snake through out. And an irregular head pattern. Everything else is individual?
Just my though that's from what Ive observed in looking through breeders of clowns. Definatly not an expert or final opinion.

Oh- and i was thinking of thise for awhile simply because i needed an excuse to say Hilarious Signature.