I don't buy in bulk yet and even I would get the crusher. Why you ask... Because when making recipies I can buy a 1, 2, 5, or even 1lb bag of something and keep it sealed then when I need 6oz, or 8oz of something I can easily measure it out at home and crush it without having to drive 1/2 hour to the LHBS. Also, if anyone is like me, I sometimes plan on making a batch, then something comes up and soon the grains are too old and I have to throw them away. If I crushed on brew day then I would never have to toss grains. In addition, I sometimes buy from my LHBS and sometimes internet. It is really hard to use the crusher from the LHBS if you are bringing in stuff you may have bought elsewhere, even if you buy from them often. I consider this improper myself and only crush grains I purchased there.
Oh, and as for crank, vs drill, vs motor... I vote for using my kids. No batteries to recharge, no motor to plug in and my arm never gets tired LOL