The page says "Receive a 20% discount on an annual NGV Individual Membership when purchasing with an American Express card until 30 December 2018." but the discount seems to apply to all membership levels.
To save online fees, call up to order tickets with your member number.
Enjoy exclusive benefits including:
Free exhibition ticket upon joining
Discounted entry and priority access to ticketed exhibitions
Members exclusive curator floor talks and exhibition previews
Programs, events, workshops and studio visits led by local artists and creatives
Annual subscription to the NGV Magazine
Up to 20% discount on NGV public programs
10% discount at NGV design stores, cafes and Garden Restaurant
15% discount on parking when you visit both Galleries
Access for you and a guest to NGV Member Lounges
Reciprocal benefits and local and interstate galleries
PRICE in title…