Go direct to traditional airline website to buy. Some of the budget airline charge for a fee for using creditcard
Jetstar => use offline payment such as SAM to pay. no incur extra charges. Or pay 711, incur 4 dollars extra charges...
Tiger => AXS incur 5 dollars payment
Scoot => During promo, you must use cc to pay, so incur 18 dollars extra charges ... Else book during non promo, no incur cc fees