Good thing there's only about 6500 pages in that catalog, or you'd be there all day looking for that amp clamp.
I have found that for some items Grainger is quite reasonable on pricing, especially if it is something you need right away, and the only options are pick it up at Grainger or order it from someone else, pay shipping and wait a day or two.
If I know I'll be going near a Grainger warehouse and there's some small item I need, I can usually order it online, show up there 20 minutes later and walk out with what I need. For some other stuff, they are a LOT more expensive than the alternatives.
I can order a sheave for $12 elsewhere that Grainger wants $65 for.