Sinto a sua dor.
Sadly PSN is notorious for not giving the developers the opportunity to put the game on sale when they want so I don't know if it will be possible. My tip for Brazilians like us is to see if you can get the game on steam, it is the storefront's policy to scale the price instead of converting. It is one of those games that can run on a potato so you might be able to play.
Right now the price on PSN is R$79.90 and R$24.99 on steam and android phones.