I suppose you measured the Lum book as well.
I think you're seriously
underestimating what an inch looks like. Trigun Vol.1 is most certainly larger than an inch (at 360 pages, whereas the Lum Perfect Collection is 400). How many other US, translated mangas are 350+ pages? And those paper stock specks are for unprinted virgin stock. Slight thickness is gained when printing is added if I'm not mistaken.
You know, this IS really stupid and trivial, but it's pissing me off that a 360 page book is "no big deal". The frelling book is most certainly more than an inch in width, and most certainly more than two frelling cm. The first thing I am doing tonoight is measuring the damn thing, and posting the width. Maybe the thing IS only 1.25 inches, but compared to most other manga I've purchased (that weigh in between 180 and 260 pages), it's pretty thick. My guess of two inches is probably wrong, but it's bigger than an inch for sure.