$200-ish for an international round-trip ticket on short flight in economy, crazy price in J, is pretty standard. Take a look at Dammam Bahrain, Brussels Amsterdam, Budapest Vienna.

On the route in question QR's economy fare is generally at the low end of the fares offered by the "natural" Vietnamese and Cambodian carriers.

For J, QR offers a very significant uplift in comfort and prestige for a modest premium over its competitors. Though I'm not sure why anyone paying his/her own way would seek that comfort , at that price, on a flight with plenty space to stretch out in Y.