I was just attempting to buy this at one of the Metro stores in the city and found that it's $20.90, which is about 10% more expensive.
Asked the checkout person and her reason was that Metro stores can't have the same price as supermarkets.
In your experience has Metro been more expensive?
Yes; they're like Woolies convenience stores. The specials are the same as the supermarkets though e.g. if a packet of Golden crumpets is $3.70 in a normal Woolies and $4 in a Metro Woolies, they'll be on special for $1.85 in both normal Woolies and Metro Woolies