I had three Sigs I sold. A 226 Equinox that has the SRT and tritium sights, a 226 Blackwater with SRT and tritium sights and a 229 sct with the SRT and tritium night sights.
226 Equinox sold for $850
226 Blackwater sold for $950
229 sct sold for $850
Had I traded these, it would have been less. A new stainless 226 is a little more than the Equinox or Blackwater if I remember correctly, so add about 75% of that difference to what I got for mine and that should give you a ballpark figure of what you could sell them for.