Fleece? To get a 40 to 50 degree rating, fleece will have to be quite thick, which means it will be quite heavy and bulky–definitely over 2 lbs.
As mentioned to you earlier, i could make you a simple summer blanket with 2.5 oz Apex (so good for 50 degrees) that depending on fabric used (i suggest Nobul) would weigh between 12 and 15 oz for under 100.
By most accounts, that's a screaming deal. It won't have the bells and whistles of a full quilt, zippered foot box, cinched up ends, straps for pads, etc, but have a extra piece of fabric on the bottom for feet to stick same in or keep out depending on preference and wide enough that you can wrap yourself in if need be. Hence why i call it a summer blanket.
Sorry, wouldn't be under 50, that won't even cover cost of materials, especially if one used Nobul. However, there won't be much of a weight difference between a blanket made with Nobul or one made with 1.1 oz ripstop nylon 2nds–a couple to a few ounces, but a definite price difference. Anyways, last time i will mention it.