The person comparing prices may be protecting several necessities with one careful decision.

Careful shopping is often load-bearing rather than fussy. A few pounds saved on one item is not about the item; it is about the electricity bill, the shoes somebody needs, the small buffer that keeps the month from becoming a crisis. From outside it can look like indecision at the shelf. From inside it is one calculation holding up several other things at once.

Be slow to read thrift as meanness or as a hobby. If you can, make it easier rather than commenting on it: name the cheaper option first, or split the bill by what each person actually ordered.