Lavishness, n.
The quality or state of being lavish.
Shades of meaning
Fernald has no entry of its own for lavishness; he lists it under excess.
Where he writes about it:
Overplus and superabundance denote in the main a satisfactory, and superfluity an undesirable, excess; lavishness and profusion, a generous, bountiful, or amiable excess; as, a profusion of fair hair; lavishness of hospitality. — from excess