Brazilian steam sells GTA V for an equivalent of 32.67 USD.
And that's currently the best price you can get if you want to buy the game legitimately. Luckily there's no region lock.
Brazil not region lock really ?
I think steam lock all region have cheap price ?
Nope, it's not region locked. You can check that in a really simple way actually and I'm surprised you don't know already.
1. Go to your local steam store by entering store.steampowered.com in a browser
2. find a game you like
3. hover over the "Add to Cart" button
4. note the number that appears in "()"

Now to check if the game is region locked,
5. Add ?cc=[country code] afte the game's link
6. hover over the "add to cart" button again
If the number is the same that means there's no region lock. If the number is not the same, that means that the game is region locked.