I get the wholesale catalog from Tek Supply
www.teksupply.com which has a host of corporate farm supply items that can be useful to the small homesteader a swell, although i have not ordered from them, they look to be a place that even a small retailer could get a good deal from [all you need is a state reseller permission tax number]. If not a reseller then their retail outlet is not to bad in pricing
www.farmtek.com
I also get the surpluscenter catalog above out of nebraska, but they wont pay shipping cost and out here in zone 5 or 6 it gets expensive on heavy items like cable.
before going to far from home you might try the case, cat and JD dealerships in Spokane as they carry wire rope for logging equipment and so forth, depending upon the size you need.
www.scroungecentral.com is the outlet for teksupply closeouts, they have a few cables that are short pieces, odd size, for reasonable price you have to d/l the acrobat files [.pdf] to see the current list so you need adobe acrobat reader installed but most floks' computers have some sort of version or another.
I just bought a roll of 3/16 for $57 from the local hardware store, so check around locally before ordering online!!!!