差 implies a kind of deficiency, so I expect
to mean A is slightly "worse" than B in some way. For example, I would expect
to imply I am slightly shorter than you. I'm not sure if this is correct, as 差不多 is also used to mean "about".
Question: Does 差不多 imply "slightly less than" when comparing quantities?
I could imagine a conversation along these lines (I made this up):
where A is grumpy that the book was 52 yuan, when B previously told A that it was 50 yuan, but B says it's 差不多 (much the same). In this context, it seems like 差不多 means "about" and not "almost". Here 52 is greater than 50, so this raises some doubt.