The expense is mainly down to Chinese vs US labour rates. How the windings are applied can make a big difference to the sound (tension, winding pattern , machine vs hand scatterwound) as can the level of wax potting - none, some, very etc. Materials used for bobbins and the wire insulation can also affect things like the overall pickup capacitance. Level of magnetic change on the magnetic pole pieces can vary as well.
In theory, it should be possible to make them sound identical, but I'm at my knowledge limit here on pickup making, so can't give a definitive answer.