They do have a nice little Sim Audio DAC @ $450 from $650 : http://www.musicdirect.com/p-97376-simaudio-moon-100d-dac-black-demo.aspx
Perhaps not as great a deal as the Wadia, but still seems decent.
The Simaudio Moon 100D DAC is only a DAC, whereas the Wadia 151 PowerDac is a DAC combined with a 50W @8 ohm / 75W @ 4 ohm per channel integrated amplifier.
When an item like the Wadia is discontinued, a $500 price on a $1200 unit usually sells out pretty fast, usually in days or weeks. Most vendors are listing it as discontinued, although a few say (on their website) that it is still available, but may or may not be in stock when you actually check. Those that haven't listed it as discontinued yet are offering it for $800, with one advertising an open box for < $700.
Steve