You must buy a coupon now for $5 and pay the balance of $15 when using it.
http://www.couponsrus.com.au/melbourne/
Wash N Shop website prices it at $35+ I guess $20 for the exterior wax that is not normally in the 'Wash & Interior'. Ref: http://www.washnshop.com/
Valid for both sedans and 4WD's
Includes complete external hand carwash and internal cleaning of your vehicle. Service includes drying of vehicle, wiping of door frames, cleaning of dashboard and console surfaces, windows and mirrors cleaned inside and out and vacuuming of seats, carpets, floor mats and boot area. Vehicle finished with deodorizer, tidy bag and tyre-shine application
Offer also includes protective wax on the exterior
Offer valid for 6 months
Hope they won't cut the corner because of cutting the price now.