When you buy a hammock for boat travel, you can chose to go for the cheapest or for a hammock to bring home. Hammocks are for sale all over with varying need for bargaining depending on the shop or kiosk and the sales person. The advantage of the "Centro de redes" is that it has the full spectrum of sizes and quality. The prices seemed fair especially after the 10% discount from the asking price it seems you can expect. If you do not buy here, at least you would leave with a fairly good idea of the variation in quality and price.
I bought a dark colored (so it would not show dirt) matrimonial sized hammock. This was a good choice for boat travel as the extra material could be folded over as a cover.
What to pay: I spent $25 US.
This is a fair organized by the local people and the city hall, it is every Sunday from 7 am to 2 pm.
You have handicraft, all kinds of art from local artists, all kinds of home made things, from clothes and jewelry to home appliances and also some typical food.
What to buy: The handicraft are interesting to buy, specially the native stuff, but there is just tons of stuff to buy.
The jewelry made of fruit peel, trees and seeds are very cute and original.
What to pay: well, I can't say really, prices may vary, depending on the product.
Anyway, but it is better to buy there than in the mall, these people are really home making those items or they have small business...
At the Market you can get anything Brazilian, from food to crafts, to clothing; for a good deal. If you are looking for something, buy it at the market, not your hotel (you can get the same things for a lot cheaper).
What to buy: You can buy anything.
What to pay: Depends on how muck you buy, but not much more than 70R$ for a bunch of stuff.