Update on this....FedEx ground got it to me in like a day and a half -- probably due to proximity, they're over in Eastern Ohio somewhere and I'm in Columbus (middle of the state) so it didn't have far to travel. Had to pay OH sales tax which added another $10 to the cost, but at ~$2.40/lb that's still only half of what my LHBS charges.
Got a large pet food storage container yesterday, and then used the first 8 lbs of the DME for a Liberty Ale clone. Left the remaining 42 lbs in the bag (rolled down tightly) and stuffed it into the pet food container....just by a little bit, it wouldn't fit, so I wrapped the whole thing in a garbage bag to keep moisture out. (Once I take another 7 lbs out for the next batch, the container ought to fit just right.) For good measure I left a couple ziplocs half-full of powdered sugar (and open) in the garbage bag to try and suck up any moisture before it gets to the DME.
Basically, so far so good, and my costs are now down under $40 instead of up near $60 ... which makes SWMBO very happy.