Neither was a mainstream hit but are by no means rare. In my experience, at least, Wild Arms 3 is dead common since it was published by Sony itself and was stocked pretty deep. The Suikoden series suffers from a title that many in the West find baffling in a genre that has always faced an uphill battle on US consoles and hasn't been pushed as hard by Konami as something like Metal Gear.
I wouldn't pay more than $10 for Wild Arms 3 and no more tan $20 Suikoden 3.