Got the opportunity to look through a relatives proof coin collection from the 1980's, and wow, all of them show a negative return on investment! Original buy price (direct from mint at the time) was recorded on the sets, and I didn't see one that showed a positive return, even when accounting for inflation. e.g.: http://www.ebay.com.au/itm/Australia-1988-Masterpieces-in-Silver-Proof-Set-/391130487435 Cost $95 in 1988, worth $76 now. http://www.ebay.com.au/itm/1982-XII...er-10-Coin-in-Presentation-Case-/131506308521 Cost $45 in 1982, worth $24 now And ditto for all the $10 proof state coins I could find. http://www.ebay.com.au/itm/1988-Australian-2-silver-coin-proof-/271931075370 Cost $25 in 1988, worth $18 now http://www.ebay.com.au/itm/1987-Australian-Proof-Set-/131540823696 Cost $49 in 1987, worth $27 no. And on and on it went. Sad.