As Edgy states, the value of $/oz silver in the ground for silver resource companies will have many variables affecting its value. Recently I have seen it as low as $0.20/oz for companies like Silver Standard, $1.30 for Pan American, $2.00 for Great Panther, and as high as $4.00 for a sector leader like Silver Wheaton.
As gwr suggested, these values will fluctuate with market sentiment, thus the current low values.
ECU is somewhere in the $0.50 to $0.60/oz silver range (debt included) for their M&I and Inferred gold/silver resources only. Hopefully with a few more months of progressively impromving produciton results and a viable scoping study we should revalue to the $1.00 to $1.20/oz range, and as high as $2.00/oz in a strong market.