I just shipped a bike from ATL to MIA, in a cardboard box. Every inch of the frame was wrapped in either bubble wrap or foam pipe insulation, and then the whole package was wrapped in a big sheet of bubble wrap. (Thank you REI's loading dock the day after they get a shipment of kayaks!)

I shipped it UPS for $28, with $1000 declared value. It took 3 days. (Edit: it weighed about 25 pounds)