Thought I'd chime in with a slightly different experience.
I just returned from Peru where as others have said, mate de coca is an everyday tea and altitude tonic in the Andes (I was in Cuzco in the Sacred Valley). Also, as already stated, you can buy approximately an ounce of leaf for 1 sole (35 cents).
I found no altitude relief or any sort of pleasure from the tea itself. I thought it tasted rather nice, better than most teas, however, I'm not a tea fan in general.
While hiking the Inca trail, I got a pretty grnarly case of altitude sickness so I busted out the leaves and chewed on them. I didn't use a catalyst like lime, or whatever you supposed to chew it with. Our guide (an idigenous Indian) didn't say it was required. The only effects I did get were a mildly numb mouth and nasty green spit. It never really helped my shortness of breath and rapid heartbeat unfortuantely. So I had to turn around and do the walk of shame. I wouldn't have made it to 4200 meters considering how I was already doing at 3060 meters.
Anyways, it was defiantely a novelty, the tea was pretty yummy, but with both preparations, I didn't get any pleasurable effects.
Oh and I didn't attempt to bring mate de coca or the coca leaf bags back to the US. Seemed like playing with fire.