You mean you're paying $1900 for the full cat back? You do know that you can get a system just as good as the stock setup made for you at a shop for less... right? I hate loud systems but I still got an upgraded 2.5" exhaust with straight flowing muffler and resonator for only around $600... including the cost of the welding and pipe bends.
As for why it stayed together from bumps on the road but came apart when you were smacking it with a wrench... Well, on the car the road noise is dampened by a large number of things: Springs, dampers, suspension bushings, motor mounts... versus getting directly hit with a rubber mallet. Try this: Replace the handle of a rubber mallet with 3' of garden hose and get a second mallet which is solid steel with a wood or fiberglass handle. Now, swinging very slowly, hit yourself over the head with each.... make sure you do each with the same speed. Which hurts more? LOL!
Thanks, I needed to go through that.