Last week I went from Manaus to Santarém by boat. I bought my ticket in the Manaus port, from a guy standing around the entrance (he looked shady but the Tourist Police told me he's an authorized seller). I paid R$90, I travelled sleeping in a hammock, without a cabin. A girl sleeping next to me paid R$80. On the boat I saw this list, saying the price of Manaus-Santarém is R$180:
Then I'm planning to go further to Belém, someone told me before the price is R$150, but the only agency I found says it's R $200 and that it's a promotion. There's no price neither in the agency nor on the ticket I had from Manaus.
Is there some official pricing list for these boats that I can reference when buying the next ticket? I'd treat the one on the boat as the official one, but I'm confused why I paid half the price.