Thanks Baggins. Good detective work.
Somebody who worked for the company told me that LSL7 outsold Grim Fandango by at least a 7:1 margin. Interview here where Roberta talks about Phantasmagoria selling a million:
One thing that really annoys me is that many retrospective articles on adventure games depict this narrative that adventure games were almost dead until Lucasarts revived them with Monkey Island and that LA then became the kings. It's such a falsehood. Any information I've seen, including from game designers at both companies, indicates that Sierra continued to demolish LA in sales right up to the end.