For that Amy Butler strippy quilt the amount of fabric it calls for it about $150 for the fabric ALONE. 16.75 yards of fabric for the front, border, backing and binding at around $9 a yard. It calls for 3/4 of a yard of 12 different fabrics plus border, backing and binding fabric (which can be fabric from the 12 different fabric called for in the quilt blocks). That is if I make it the size the pattern calls for (60.5 x 76.5) a twin is normally 68 x 88. If you wanted to use the quilt folded up on the bottom of the bed with a duvet as the comforter then the original size would be fine.
To quilt the quilt it would normally cost you $120 (68 x 88), I don't even know how much I would charge to piece the quilt, I have never figured out how long it would take me to piece a quilt (that includes cutting it all out which sometimes takes longer than sewing the quilt top). Also every quilt has different difficulty levels. Then you have the batting (for the size of the quilt it would be around $20), then to attach the binding and hand-sewing it to the back would cost you around $63. That is actually pretty cheap as hand-finishing the binding takes friggen FOREVER. Plus the cost of a spool of thread and you can see how much it can add up. This all adds up to $353 not including my time to make the quilt top, sew the backing and the thread. So you can see why it doesn't make sense for me to sell quilts, why would someone spend that kind of money for a quilt that I made when they could buy a commercial quilt for less than half the price? The only area I would make money is in quilting a quilt as that is purely my time and thread (someone already made the quilt top and provides me with everything except for the batting).
Twin quilts:
A twin mattress (in the US) is 39" X 75". How big you make your quilt depends on how much you want to hang down on both sides and at the end, and whether you will be going up over pillows at the head of the bed.
Most twin comforters (minimal overhang) is 65" X 88" and bedspreads (large overhang) is 81" X 107".
If you want something in between, you would go with 70"x 90".
So if I add a row of quilt squares to both the length and width it makes it approximately 69 x 85. I could make the border wider to make it bigger as well. Both of these options would take a little more fabric. The Amy Butler strippy quilt uses muslin for the base of the strippy quilt which I did not include. Muslin is cheap (which is not included in the fabric price) but I like paper piecing better anyway. This quilt seems to require a lot of fabric, more than I thought. It calls for 12 different fabrics at 3/4 of a yard, then you have 2 yards for the borders (more if you make it bigger, 4 2/3 (I rounded up to 5) yards for the backing and 3/4 of a yard for the binding. IT calls for 3 1/8 of a yard of muslin, muslin cost like 1.99 a yard but like I said, I like to paper piece rather than use muslin.
I found another strippy quilt that doesn't really have a "pattern" and it doesn't have a fabric requirement list. I like the white between the squares. I don't know how much fabric I would need for the quilt. I would have to "wing it" and order more if I needed more. I can tell you that it would end up less than the AB pattern.
LINKThis one is cute too (not a strippy quilt):
LINKI probably wont know the exact cost of the fabric until I am done. If I do the strippy quilt I linked to there is no way to tell for sure how much fabric I will use until I am done. Any left over fabric I can figure out something to make with the rest. I can say that it wont be over $150 (I wont charge you for the batting or anything else). Most people wouldn't even want to spend $150 on a quilt (again that is just the cost of the fabric) let alone what it would cost to have someone make it from start to finish.