This game dosn't have quite the same budget (but I'm not saying it's a small one) as the bigger games and those games can get away with their price - because people will buy it non the less (over-hyped, super-marketed AAA-shooter sequel no. 6 with the well-known developer and brands on it).
RO2 and TWI is less famous (as of right now) and has to attract more buyers with it's reduced price, who would otherwise be reluctant to pay for a game they do not know much about, when they could just play it safe and go for the above mentioned AAA shooter instead.