Also consider rigid card envelopes. You can post up to A4 sized items as a large letter (as long as under 500gm and total thickness is under 2cm) so the maximum cost would be cost of packaging plus $3.00 postage. Some fabrics would probably not be able to go this way, so if looking for a uniform postage method it might not be convenient, but for lighter weight, thinner fabrics or short lengths etc that can be folded to fit (in a zip lock bag with all the air out, so essentially vacuum sealed), it would be a cheaper alternative (but no tracking / proof of postage unless you pay for registered, or have some other method for gaining verifiable proof of post).