Not sure I would agree. The Piano series has the piano and sample synth engines, where the Electro adds one more engine with the organ, along with the physical controls. I would speculate that has to factor into driving up the cost. Where the Electro could cost Clavia a bit less is in the keyboard mechanism itself. If they stick with the HP action (hopefully using the TP-110 and not TP-100), it could be less expensive compared to the HA action in the Piano and Stage models. I'd gather that the SW action is less expensive as well, which is how the Electro could keep a price point below the Piano.
It depends on a) whether they come out with a new Electro and b) what features will carry into it from the Stage 4, Organ 3 and/or Piano 6.
My guess is that the new Electro will not include two piano and two synth engines, but rather one each, which helps position the Electro as a more affordable option. I guess we'll see.