Looks like a price error. I got one today and the guy at the counter didn't really care. This is currently in their catalogue for $20.91 and they've got yellow stickers in-store with that price as well but when scanned at the counter or if buying online it'll show as $12.91.
This is the best wheel cleaner I have tried so far. It dissolves brake dust and grime really well. This most likely will be too strong for alloy wheels so make sure that it's compatible with your wheel before buying though.
If you're buying more Meguiar's stuff, don't forget that Repco is currently doing 35% off Meguiar's chemical range and SCA will beat any competitor's price (50c for items <= $50; $1 for items > $50) plus with a min $50 spend, you can get a $10 cashback.