Alternative: make tomestone costs unlock a whole slot instead of a role piece. Example: pay 800+ tomes on the chest piece, unlock all chest pieces for that specific tome set. That way, once unlocked, any alt role can get the piece for free or a small sum of money. Costs can be adjusted with this in mind.

More reasonable alternative: introduce a decreasing cost to slots. Example: pay 800+ tomes on the chest piece (and can rebuy it for free). Pay 400+ tomes on the next chest piece of another role. Then pay 200+ tomes on a chest piece for a third role. Then 100+, etc.