Time for another (possible) BWS price error!
Asahi Super Dry Black bottles are on special for $2 each at BWS (despite a case of 18 usually costing $68).
So just add 18x single bottles to score a case for $36.
Other possible steps:
Combine with 10% Cashrewards.
By purchasing 2 cases (36 bottles) I was able to combine with a (possibly targeted) 1000 Everyday Rewards points (equates to ~$5) for $70 spend at BWS.
With either or both of those additional steps, two cases will ultimately cost you $60-$65, which is lower than the usual single case price!
Edit: Stock levels are getting hit. If it shows as unavailable, try changing to other stores nearby and you might find more stock.