Your favorite quilt shop re-orders the black fabric you want because there's not enough on the bolt to suit your project. Every time you go the shop---with a full wallet I might add---they haven't gotten it in yet. But when you don't have the extra funds and can't make the 45-minute drive out to the quilt shop, you get a call saying the fabric came in.
And of course, least in my case, it HAD to come in a few days before the shop was having a 20% sale on all fabrics! Which I couldn't take advantage of at the time.
When planning out your quilt, you put shrinkage into account and later realize you didn't have to add on the extra yardage. Probably have enough fabric to make a table runner or two. The ONE time you don't account for shrinkage and you have to go out buy more fabric because it shrunk too much and you're a few pieces too short.