I'm a fan of bestbullysticks.com - very large selection of natural chews and the best prices I've been able to find, especially when compared to pet store prices. We regularly buy their "Jumbo" 12 inch bully sticks, usually 100 at a time. It takes Roux about 20 minutes, and Knox about 45 to finish these off. I saw they had a new "Monster" 12 inch bully stick the last time I went to order our regulars. They're a little more expensive than the "Jumbo," but I wanted to give them a try so I ordered 20 of them. Holy cow, they're HUGE. You'd never find one this thick in a pet store, and if you did I imagine they would charge $20 or more for it (they were $5 each through bestbullysticks.com). It took Roux about 45 minutes, and Knox had to take a break after about an hour and finished it up the next day (another 45 minutes or so).
Also, they sell giant elk and moose antlers for cheap. I just ordered 2 elk antlers that are seriously as thick and long as my forearm, and they were only $20 each. I've seen pet stores selling carrot sized antlers for at least that much before.