This past summer Aldi rolled out a new line of baby products including training pants in 3T/4T size. We have been using these for nighttime with out preschooler until recently when he completed potty training. They are priced at $5.99 a pack in our area making them $.26 per "pull-up." Target's Up and Up come in at $.32 and Walmart's Parents Choice at $.31 making Aldi's s substantially cheaper.
I believe these are comparable in quality to Pull-Ups and any of the house brands at local stores. They are not meant to substitute for a diaper, so they are not totally leak-free if you have a heavy overnight wetter, but they do help make that transition at training time from diaper to underwear.