I have a good friend who makes tie quilts (mostly wall hangings) and she says its tricky because of the fabric being cut on the bias she puts a cotton backing on it so it wont stretch. It also makes the project heavy. She also goes to thrift stores and garage sales to get her ties. Once in a while a bag of ties just turns up on her front porch. Sometimes she will do a pillow or wall hanging as a memory project after someone's grandpa passes away.
Estate sales often have ties but may be more pricy because of sentimental value.