Do tourists pay more than locals III?

I am currently visiting Brazil to do some work on a competition issue. My host and I had to travel to Brasilia for some meetings. We landed and he called for a taxi. While waiting, I noticed a long line of taxis waiting for clients and asked why he needed to call. It turns out you get a discount of ~20% by if you know how to order a "radiotaxi," something with which most tourists will be unfamiliar.