I highly doubt those grinders will sell for those prices, but you never know.  My dad sold his SDM-4 a few years back for $1800.  I seen another mint one sell for the same.  I sold my well used one a couple months back for $800 (looked about like the one listed for $2000)
If you think the markets there, id go for a SDM-4 or a improved RSII.  Is there really that great of a demand for chain grinders?  Not a lot of hand falling going on compared to 10 years ago.  Plus, if I was in the market for a grinder, there is nothing wrong with a Simington.  I know a lot of professional cutters using them.  I feel like part of the reason guys want the Silveys is the history behind them.  That’s what my old man used, I remember being out in the shop grinding chains with him when I was just a little kid. 
The thing the Silveys got going for them is that they are really consistent and super smooth!  
I have a Madsens catalog from 2008.  Pro Sharp is listed at $2099.