i think the best value for money set of strings are D'addario's normal 10s or 9s... its because of the hexagonal core of the wound strings... even if it rust (only the core rust cuz its steel), the rust have space to fill the gaps between the 6 flat surfaces of the hexagonal strings and the wound nickel...
for other brands where the wound strings are round and touching the wound nickel coil, when it rusts, the rust would build out of the coil and u'll see ur wound bass strings as if the nickel outside were rusting (but its not the case, its the steel core, nickel don' rust, they just oxidise to a dull silver)
there's no cheat for treble unwound strings though...