Since there aren't any other Shaefu eggs for sale at the moment, I'd look at the prices of other CS eggs. Right now, it looks like they're going for between 75 and 100mil (Ezahni, Jahra, Saruka). The Jahra egg is 75 mil, probably because it's still available in the Cash Shop, so 90-100mil seems more accurate for other eggs.

This would be how I would decide pricing personally, but you can always ask the SB too. They know everything!