Checking dagger prices on Johnson's is like checking Garandprices on Duff's. Johnson is one of the top dogs and commands a premium just like Duff. Typically a private seller is not going to get those prices.
Back to your dagger, what you have is a SA handle, scabbard and hanger. The blade and lower crossguard are SS. The upper crossguard could be either. If it has the same internal casting marks as the lower crossguard, then I would say SS. The maker of the blade is an uncommon maker, which would bring a premium over a common maker. It appears as if the dark burnishing has worn off the inscription which would bring down the value a little. As Jim said above, the three daggers together are worth far more than $1000. Do you have pics of the other daggers? I used to collect these, but have gotten away from it for a while to concentrate on Carbines and Garands, so I'm not up on the current values. If they are for sale, I may be interested.