And if you take E11, the cost drops to HKD20 I believe.

E11 would go thru Tung Chung first before heading out to HK Proper. It adds about 10 to 15 minutes to the ride normally as there are locals / airport employees using the E11 at the first few stops.

Alternately, Bus S1 costs HKD1.50? or some dirt cheap change to get you to Tung Chung where you can take the regular MTR, a fraction of the cost versus Airport Express and about the same as A11 but quicker than A11 / E11 which of course does not require any transfer between Bus and MTR.