The Collaborative International Dictionary of English v.0.48:

Sumptuosity \Sump`tu*os"i*ty\, n. [L. sumptuositas: cf. F.
   somptuosit['e].]
   Expensiveness; costliness; sumptuousness. [R.] --Sir W.
   Raleigh.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sumptuosity
    n 1: the quality possessed by something that is excessively
         expensive [syn: lavishness, luxury, sumptuosity,
         sumptuousness]