If the cost indeed is reduced by $1 bn, then airplanes delivered will have less features on them.
If you really want to reduce the cost, just order 2 vanilla 747-8i. Maybe add GoGo so the president can stay in touch via Twitter. That way you don't need the extensive secure mission communications system, missile defense, aerial refueling, VIP suite, medical facilities, and who knows how many and what other features probably envisioned originally.
Better yet, just charter an airplane from an airline whenever you need it. You get what you pay for.