I don't understand this price disparity

i saw a promo Cathay Pacific was running with DBS cards and book a ticket to Taipei via Cathay's online booking website on 8 Aug. The condition to enjoy the promo was payment had to be made with DBS cards.

i was randomly checking my mail today 14 Aug and came over a zuji promo for airfare to Taiwan. as i was curious of the deal, i took a look. to my surprise, for the same traveling dates, flight and payment condition, zuji offered a better deal. S$14 cheaper. i looked over my e-booking confirmation which Cathay sent me, scouting out for a cancellation option with full refund but found none.the taxes and surcharges are the same for both sides so it boils down to the cost of the air ticket. Cathay charges S$352 whereas zuji, S$338. how inconsistent can prices get over different sales platform? and don't think that you always get it cheaper direct from source. its quite a fallacy from this experience isn't it? i guess i just have to suck it up and count as a case of bad timing.