I was looking at flights on FlyScoot flying out on the 10th of July and found a price of $239 plus 20kg baggage making it $273. I booked through STA Travel for $224.96 and it already includes 20kg baggage.
You can save even more if booking for another date as the price remains at $224.96 but the price on Scoot could show $279 not including baggage.
Did you confirm in includes luggage?
It looks like it does because it isn't a 'seat only' fare.