Data General One
This was probably the first true laptop PC (as opposed to the IBM "Portable PC" which was available at the time.)
It could operate from batteries, could accomodate 512K of RAM, had a full display and keyboard, and dual floppy drives. It sold for $2895, which today would be around $5800.
Until then, Data General was known for their minicomputers lines such as the Nova and Eclipse, and was a competitor of Digital Equipment Corp (DEC).