The price of my labor for making a t-shirt quilt will vary, based on the features of the t-shirt quilt. A good estimate for preparing a higher quality t-shirt quilt is about $10 per t-shirt. That includes ironing on the interfacing to stabilize the t-shirt material, cutting out the t-shirts and fabric needed for the top, sewing sashing and border material to the t-shirt squares, sewing the t-shirt top together, preparing the backing and batting, completing the quilting, and finishing the quilt with a double-fold binding. See the first attachment for an example of this type of quilt.
I can also prepare the t-shirt quilt without sashing and with a fold-over style binding. This involves less labor on my part. The cost estimate for this type of t-shirt is about $8 per t-shirt. It is possible to use fleece material for the backing and not use batting, which makes the cost even less. See the second attachment for an example. 
I would need to meet with you to see your t-shirts and talk to you about the features you want and the finished size of the quilt you want to give you a better estimate.
The labor price for 15 shirts can run from $105 to $150; for 20 t-shirts from $140 to $200, and for 30 t-shirts (which would make a double size quilt) from $240 to $300.
You are responsible for providing the fabric and materials to make the t-shirt quilt: interfacing, 1 to 2 yards of fabric for the quilt top, batting, 4-5 yards of fabric for the back, and quilting thread. You can buy the interfacing and the batting at a reasonable price from me. When I know how many t-shirts you have, I can give you an estimate of the cost of the fabric and materials.
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