I sold a bunch of 4-legged cabinets before I moved. I got the lawnmower boxes from Lowes, Home Depot, and people's yards on trash day as free boxed to ship them in. Take the legs off, wrap everything appropriately, tie the lids and doors down so they can't open in transit, and they are easy to ship.
eta: Also, I use that flat-sheet styrofoam insulation to ensure that the cabinet doesn't get gouged up in transit, too. I shipped a Queen Anne cabinet and stool from WV to West Coast by FedEx Ground and it arrived in perfect condition. I use it for shipping the sewingm machine head, too. That rigid foam works well to keep large things from digging out of cardboard boxes.
That's too much work for me:> I will have to stick local if I decide to part with them.