conspicuous austerity
n. Spending large quantities of money on goods and services that convey an image of simplicity or austerity; a lifestyle in which a person openly and deliberately uses goods and services that convey a lower socioeconomic status.
Conspicuous austerity? Joan Kron is credited with coining the term in 1983, in her book 'Home-Psych.' It's partly about voluntary but expensive 'simplicity,' like people going to Buddhist retreats 'where they give you no food, the surroundings are Spartan, they beat the daylights out of you with exercise and deep-tissue massages and they charge you a lot of money.'
—Bill Dunn, “Reduced consumerism may be ephemeral change,” Capital Times, January 08, 2002
When Joan Kron presented her seminar, 'The Psychology of the Home,' for interior designers during the annual fall furniture market here, she pulled no punches. … Other status symbols are products of conspicuous consumption of materials such as superfluous curtains around the four poster bed or, in the other direction, conspicuous austerity.
—Mardi Epes, Arkansas Democrat-Gazette, November 01, 1984
1975 (earliest)
Characteristically, the Fed's one touch of conspicuous austerity makes it even less visible: under Burns, the fleet of limousines has been replaced with compact Valiants.
—Larry Martz & Rich Thomas, “Burns and the Fed — Feeling the Heat,” Newsweek, March 10, 1975
This phrase is loosely based on conspicuous consumption, which American social critic Thorstein Veblen introduced to the language in 1899 (in his book Theory of the Leisure Class). See the Word Spy entry for inconspicuous consumption (which is almost synonymous with the second sense of the definition) for more on this. A close synonym for this phrase is downward nobility, which entered the language in the mid-80s.

The first citation credits Joan Kron with coining this phrase, but that appears to be true only for first sense, as the earliest citation shows.