QuindoMe too buddy. This is one of the best ways for me to get a box considering my local card shops charges $140+ for a box, and then tells me that I got it cheap. :/
Redleader$140 makes the smallest of margins on it when we purchase from a supplier. For us a box generally costs $110 before GST and shipping, and normally works out to be $134 with those inclusions. When you factor in overheads for running a store, wages, etc, it doesn't add to much margin on each purchase.
The big difference between sourcing the cheapest online price possible, and purchasing from a supplier, is from a supplier we get after sales support, and competitive play support. If we didn't buy from a supplier we wouldn't be able to hold pre-releases, or tournaments with prizes. So yes, you're paying more per box by going into a store, but you're supporting your local store and gaming community by doing so.