> The register would lookup the prices.

Not in the 1970s and early 80s. Do you know what computers costed back then? 1 KB of memory was as expensive as the whole cash register used by Aldi/Lidl. And there was no computer networking whatsoever, not even between multi-million super computers. When the German railways introduced computers at the ticket windows in the 80s all ticketing data was stored on 8 inch diskettes. And if you bought a not so common ticket the agent had to swap the diskette first.

I don't think Aldi/Lidl used diskettes at their cash registers. Maybe when scanning started in the mid/late eighties, but they certainly didn't have to swap during the day.