The cost would certainly be higher than that of the X1000 if we are looking at a multicore CPU at the 1.6HGz+ range.
The laptop/notebook motherboard would be a custom design with a smaller production run than the X1000. The custom design would either have to include an onboard compatible AMD (ATi) GPU, or if it went with some obscure but low cost embedded part then there would be the additional cost of the graphics drivers.
Not sure where people stand on the Xorro slot and would they consider the laptop/notebook less of a modern Amiga without a Xorro slot. If A-Eon released a portable without the Xorro slot they would be signalling that it is not part of the standard set of features.
What about other expansion ports like PCMCIA or ExpressCard 3/4?
Then there is the battery support in OS4.x, including sleep/deep-sleep support, power control.
Web cam, Wi-Fi, Bluetooth, custom A-keys reduced keyboard, and touchpad support. Sure, some of this has already been done by Morphos and could be reverse engineered under license by A-Eon but all this extra work would be part of the development cost which would inadvertently become part of the laptop/notebook hardware cost.
At the end of the day it is all possible, it just seems so impractical.