Another thing to consider is that real stores will deliver stuff without you having to run to them and pick through piles of lumber to find good stuff etc.
I did a deck on the house and emailed a list of materials to the local lumber yard and they delivered it. Every piece of lumber was good quality. The neighbor is a big box fan and they have him trained that they are the only game in town. He saw the quality of the lumber and remarked "you must have been at the depot all day picking these out?" . I got the deer in headlights look when I told him the local lumber yard had picked and delivered for me.
I have a rental apartment and the boiler failed under warranty on a weekend. I called the local family owned plumbing supply house and spoke to one of the sons. He asked if we could have the boiler disconnected in the next two hours so he could pick it up when he dropped off a replacement (at no charge).
Do you know any big box store that would do that?