Reserved Terms?

It seems that, somewhere along the lines of my cultural acclimation, I have come to associate certain expectations with the term "custom". And, while I realize, at a rational level, that "custom" is a fairly generic term, I can't help but think of the various TV shows centered on "custom choppers", "custom hotrods" and the like.

Today, I got a sandwich from the Wholefoods sandwich counter. I got one of their daily specials. However, Wholefoods frequently uses red onions, which I have an allergy to, on their sandwiches. Indeed, such was the case for the specialty sandwich I wanted to order today. Thus, I asked the sandwich-maker to substitute raw white onions for the grilled red onions that are part of the sandwich's normal recipe. Now, I don't know whether it was this substitution that warranted it or that it was a daily special, but, the price label on my sandwich's bag said, "custom sandwich". Seeing that label almost immediately prompted me to wonder if I should expect the sandwich in the bag to have some kind of flame paintjob or ridiculous amounts of chrome.