Prismatic Eye, Prismatic Aura, and Prismatic Bow all give precedence for a prismatic thing doling out it's rainbow one color at a time, in the same level range as the basic Spray without extra cost. 1/day is 36,400 for 7th or 48,000 for 8th. The other bonuses are worth a total in the same range, meriting some small markup for multiple functions but not very much since you lose them as you go, the only standout being +2 luck on non-magical attacks. The whole item is a gimmick based on an offensive ability with a set save DC, so should get the same price slashing treatment doled out in the MiC to make those worth keeping.

No more than 50k, 40k would be better. I'd also change the amethyst ability to something that matches the rest like +2 deflection vs melee attacks, though you might decide that makes it a bit too pedestrian.