The Savage 24 O/U's are WAY overpriced in my opinion. I was "into" them for a while and I had a few. Savage just never seemed to get them canted correctly so that the POI was similar in both barrels.
The first one I bought was a 12/22 hornet, and if you sighted the hornet in at 50 yds, the 12ga was about a foot low.
To answer your question, a used Savage 24 is worth $3-500 depending on what it is and what condition it is. The 20ga/22 you have is not one of the higher valued caliber combos in my area.
Now I just realized that the person posting has 1 post...and probably will never read this. Another wasted 5 minutes...LOL