The market price is probably between $400 and $800. The low side for a very ordinary mixture of USGI and Italian-made parts on a rifle as sold by the Danish and resold by Alan Lever et al. The high side would be for a 100% matched (ie only Italian parts in a Breda or Beretta, and only USGI parts in a WIN, SA, HRA or IHC) and in good shape. The HRA and IHC guns are scarcest and they were in Canada before the flood.
Your SA is the largest production volume of any maker, so for $600 I would want to see no Danish serial number on the stock or bolt, no gouged or oil soaked wood, but still properly USGI marked, and a US barrel not a Danish VAR or Italian BMB or BMR barrel.
Is this unreasonable? No. There are thousands of Garands in Canada.