Unless you're looking for match ammo, the least expensive .22 is usually milk cartons at walmart.
Cabelas had a good price on Federal 375 bulk packs last fall, at $9.99 each with free shipping, and that's the only time I've found it cheaper than at walmart. Local walmart is around $20 per 550 after tax. Cheapest case deal gun-deals.com shows online is J&G sales, with a case of 5000 for $200.32 delivered. To do much better than any of that, you'd need to order an actual truckfull. This site
http://gun-deals.com/ammo.php?caliber=.22+LR is linked in the sticky at the top of this forum, and is your friend for current ammo pricing and availability.
best deal I've gotten recently at Cabela's: 375 for $9.99 delivered is 2.664 cents per round
everyday price at my local walmart: 550 for $20.00 (after tax) is 3.636 cents per round
best case deal I can find on an aggregator site: 5000 for $200.31 is 4.006 cents per round
You let me know if you can even find a deal at 3 cents a round, delivered - I and the other forum members would appreciate the heads up.