The Collaborative International Dictionary of English v.0.48:

Lavishness \Lav"ish*ness\, n.
   The quality or state of being lavish.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lavishness
    n 1: the quality possessed by something that is excessively
         expensive [syn: lavishness, luxury, sumptuosity,
         sumptuousness]
    2: excessive spending [syn: extravagance, prodigality,
       lavishness, highlife, high life]

Moby Thesaurus II by Grady Ward, 1.0:

137 Moby Thesaurus words for "lavishness":
   Babylonian splendor, abundance, affluence, ample sufficiency,
   ampleness, amplitude, avalanche, bonanza, bountifulness,
   bountiousness, brilliance, bumper crop, carpe diem,
   conspicuous consumption, copiousness, deluge, dissipation,
   elaborateness, elegance, embarras de richesses, enough,
   extravagance, extravagancy, exuberance, fertility, flood, flow,
   foison, full measure, fullness, generosity, generousness, glory,
   gorgeousness, grandeur, grandiosity, grandness, great abundance,
   great plenty, gush, imposingness, impressiveness, incontinence,
   intemperance, inundation, landslide, leaking purse, liberality,
   liberalness, loose purse strings, lots, luxuriance, luxuriousness,
   luxury, magnificence, majesty, maximum, money to burn,
   more than enough, much, myriad, myriads, nobility, numerousness,
   opulence, opulency, outpouring, overabundance, overaccumulation,
   overbounteousness, overcopiousness, overdoing, overdose, overflow,
   overgenerosity, overgenerousness, overlavishness, overliberality,
   overluxuriance, overmeasure, overmuchness, overnumerousness,
   overplentifulness, overplenty, overpopulation, overprofusion,
   oversufficiency, oversupply, plenitude, plenteousness,
   plentifulness, plenty, plethora, plushness, poshness,
   pound-foolishness, prevalence, prodigality, productiveness,
   profligacy, profuseness, profusion, proudness, quantities,
   reckless expenditure, reckless spending, redundancy, repleteness,
   repletion, resplendence, rich harvest, rich vein, richness, riot,
   riotousness, ritziness, scads, shower, spate, splendidness,
   splendiferousness, splendor, squander, squandering, squandermania,
   state, stateliness, stream, substantiality, substantialness,
   sumptuousness, superabundance, superflux, teemingness, waste,
   wastefulness, wealth