I think that the cost of make your own diapers can be prettymuch whatever you decide. I've diapered 2 girls(mostly "new" dipes for each due to circumstances) for the cost of a couple packs of elastic($1 packs from joaannes??) a pack of sewing machine needles and a pack of sew on velcro stuff. I started with my own fabric/scrap stash and put the word out to a few people. I have gotten SOOOOO much fabric, in the form of clothing, sheets, blankets etc that i'm moer than set fro my 2 girls(one who only needs them at night woohoo!!) and am making more for LO on the way in May. If its a boy i'll likley buy either atotal of a yard or 2 of fabric thats "BOY" (i never pay more than $1 a yard)
I even had a woman at church give me 10+ skeins of yarn(wool, alpaca and a pink fuzzy cute one) she had wanted to learn to knit but after it sitting 5yrs decided i could use it better. I made a skirt for her DD out of the fuzzy pink
I've also made diapers for friends those who plan to CD and even a couple who ddint plan to but wern't aposed to having them for "back up"...which i found out one uses them more than expected "cause they aer just to cute to not use!
Dont be afraid to ask around... people are cleaning out closets all teh time and someone in "need of junk" often gets peole looking they feel good for helping and declutering and you feel good saving money!
I dont think i've spent more than $20 a girl including the electricity and all! But I certainly COULD spend FAR more with tha cute things out there! and ther really NICe fabrics and such.. not to mention the wool yarns and such too.