Sorry ... more.
I had a problem of needing a longer steerer on a pair of forks. I decided to work on the existing forks rather than just cast them aside. They went off to Swallow, and they cut off the existing steerer at the crown, then reamed out the crown, then welded in a new 531 steerer. Of course that gets the crown jolly hot, so you would lose the nickel finish on your forks, but Swallow also could powder coat them black, for example.
So there are different options. I note in the photo that the steerer has splayed out slightly....was the headset difficult to get off? Tight and tough to turn? If not, then I would certainly try getting the crack repaired.
Finally....why did it crack? Probably someone put in the stem insufficiently into the steerer, then overtightened the wedge, which exerted undue pressure on a relatively weak part of the steerer. with everything apart as you have it, you might look at how far the stem quill goes into the fork, and where the wedge splits. If the thread is still OK, ie not too tight, and the crack is way above the point where the wedge engages in the steerer when everything is in properly - ie deep enough insertion of the steerer - then brass brazing the crack may be fine. And cheap.
Does that make sense?
Tim