The are 7 different ways across 3 unique modes of transportation to help you travel from Araruama to Arraial do Cabo. If you're only considering the price, you should check out the bus out of Duque de Caxias towards Cabo Frio, as it is the cheapest to Arraial do Cabo. It's common to find tickets for as low as $17. Autoviação 1001 operates from Araruama to Arraial do Cabo, so you book your trip with them! Book as soon as you can, as there may be limited availability.
On your trip from Araruama to Arraial do Cabo, it is best to book as soon as possible. It won't necessarily help reduce your price by a large amount, but will ensure that you have a spot on the bus or train.