I don't know what your market is like, and I don't think I have ever seen a Toro tool before, but if I were to compare it to say a Delta Homecraft of similar size and age, I wouldn't expect to pay more than $50 or $75 if it was especially nice. Given that the return spring is broken, I don't know that I would want to pay much at all for it. Is it going to be a part that you can fabricate yourself or something that you could turn up on eBay? If I were the seller and trying to move it on Craigslist, I think I'd feel really good getting $20 for it and would take less if I got a serious offer. Otherwise, around her at least, I would expect it to sit for a long time.
For comparison, the basic 1950's era Craftsman 100 drill press sells for $100 to $150 around here.