Note that each Carrefour might have different prices: not sure about whisky but in general this seems to happen a lot.

Also, RT-Mart usually beats Carrefour on prices: their locations are not that convenient for most visitors and the choice of imported food is much more limited but as for Kavalan products they probably have the same range so it might be worth checking out.

Last but not least, there are also Kavalan's own shops (listed here), which should offer more choice than the supermarkets. If I remember correctly you can get a lifetime 5% discount for spending over 6,000 TWD at a time (or perhaps it only applies at the distillery, not sure).