The table on Item Creation gives the cost for "Multiple different abilities" for slotted items as "Multiply lower item cost by 1.5" There is a warning on the webpage Altering Existing Items warning against moving powers from one slot to another, especially inappropriate locations.As with all things non-PFS it is up to the GM to say, but expect the price to be 50% higher than the head slot, remembering that normally you can only purchase even bonuses to stats (+2, +4 or +6)
That's what I was looking for. I couldn't find the reference back to it and wasn't sure if it existed in the final ruleset. I remember it being a specifically discussed change in the Alpha.
Not trying to break the game or buck the system. Amulet of Spell Cunning/Mastery it is!