I have heard that oxtails are the gold standard for Asian beef broths. For example, most of the ph'o recipes call for an oxtail broth enriched with lemon grass.
Oxtails are very expensive, though. In my neighborhood, they run about $4-6/lb. That means that a decent sized pot of oxtail soup would costs about ten bucks.
What is so special about the tails? Can I substitute cheaper beef parts with similar results? I imagine the tail has a lot of collagen, which might give the soup extra body. But is the flavor of oxtails different?