Cbus art collection sells well but what was the ROI to members?

At the same time as the Australian Prudential Regulation Authority (APRA) has been urged to pursue greater transparency around superannuation fund unlisted investments, major industry super fund, Cbus, completed the $9,892,677 sale of its art collection.
The auction house, Deutscher and Hackett, announced the sale of 100 lots, noting that 96% had sold by volume with 145% selling by value.
Cbus has been one of a handful of superannuation funds to maintain an art collection – something which has generated interest in terms of how the sale proceeds from the auction translate in terms of an overall return on investment.
According to the auction house, the Cbus auction was significant not least because five new artist auction records were realised: Margaret Preston, Coastal Gums, 1929, also known as Australian Gum Blossom ($613,636): Godfrey Miller, Trees in Quarry, c.1952 – 56 ($466,364); Eveline Syme, Tuscan Landscape, c.1930 ($147,273): Bernard Hall, In the Studio, c.1924 ($73,636); and Arthur D’Auvergne Boxall, Building of the Sydney Harbour Bridge, 1930 ($46,636).
The following represents the top 10 results from the auction:
SIDNEY NOLAN
Crossing the River, 1964
ESTIMATE: $600,000 – 800,000
SOLD for $1,080,000 (inc. BP)
ARTHUR BOYD
Shoalhaven Riverbank and Large Stones, 1981
ESTIMATE: $250,000 – 350,000
SOLD for $613,636 (inc. BP)
MARGARET PRESTON
Coastal Gums, 1929
also known as Australian Gum Blossom
ESTIMATE:$180,000 – 240,000
SOLD for $613,636 (inc. BP)
GODREY MILLER
Trees in Quarry, c.1952 – 56
ESTIMATE: $150,000 – 200,000
SOLD for $466,364 (inc. BP)
WILLIAM DELAFIELD COOK
Hillside, Ellerston, 1990
ESTIMATE: $150,000 – 200,000
SOLD for $454,091 (inc. BP)
RUSSELL DRYSDALE
The Fossicker, 1949
ESTIMATE: $300,000 – 400,000
SOLD for $429,545 (inc. BP)
JEFFREY SMART
Children Playing, 1965
ESTIMATE: $200,000 – 300,000
SOLD for $368,182 (inc. BP)
ARTHUR STREETON
Balmain and Leichhardt, from Holtermann’s Tower, c.1921
ESTIMATE: $250,000 – 350,000
SOLD for $294,545 (inc. BP)
FRED WILLIAMS
Sapling Forest, c.1960 – 62
ESTIMATE: 180,000 – 240,000
SOLD for $282,273 (inc. BP)
ROSALIE GASCOIGNE
Lasseter’s Reef, 1993/1996 – 97
ESTIMATE: $150,000 – 200,000
SOLD for $245,455 (inc. BP)
So what’s the CAGR?
Looks positive, but without knowing their purchase prices and how long they’ve held them, the figures are meaningless.