Most people pay more. I'm not sure why--bargaining skills? Season? Different boats? I paid more for Belém to Macapá, which might be relevant or not. Most people will pay more than Tobi did for his bike, too, since most of us are on bigger bikes with more baggage.
My memory is hazy, but I remember something like 125 reais for a hammock, twice that for a cabin for the one-day ride to Macapá, with about the same amount again for a fully-loaded KLR. YMMV, and again please note this was a different route from either of the ones you're asking about.