Is there an upholstry shop or drapery shop near you? I bought a HUGE bag of fabric that was stuffed with approximately 1/2 yard pieces of the fabrics you typically see on mid to upscale restaurant or hotel seating...for $10. The bag was about 'hugging size' and approximately 6 feet long. My friend and I split it and I ended up with a medium size tote (the ones that were on sale after Christmas for $3-$4 at Wal-Mart) full of fabric after I folded it up neatly...and had already passed some on to another user and also had set aside a good sized bagful for a lady who wanted to make cushions for her dining room chairs.
If I had purchased those fabrics by the yard, I would have had to pay $100-$200 for them at fabric outlet pricing, not even regular retail.
If you could find something in your area where you could get this kind of deal, then you would be able to basically be charging only for your time instead of it all going to the price of fabric.
Keep an eye out and you'll be able to find a good deal, I'm sure.