While it's certainly possible to get a good buy from Chemist Warehouse you do need to check the pricing with competitors as they often do a "Kathmandu" ie. propose a RRP price that while legitimate you'd be silly to pay that price for the few days it's there rather than at a cheaper price from one of their sales (or from a competitors sale).
Here's an example: Cenovis Sugarless C 500mg - Chewable Vitamin C - 300 Tablets
At Chemist Warehouse it's currently on half-price sale $12.99, $13.00 Off RRP ("Don't Pay RRP: $25.99") https://www.chemistwarehouse.com.au/buy/47377/cenovis-sugarl…
At Woolworths it's on special this week for $12.60 Was $15.00 https://www.woolworths.com.au/shop/productdetails/88038/ceno…
At Coles it's regular price for $15.00 https://shop.coles.com.au/a/national/product/cenovis-tablets…
So despite the Chemist Warehouse half price sale it's actually cheaper to get it from Woolworths where you are saving $2.40 (rather than the claimed $13.00 off at CW). Also the current CW sale ends today (26/9) and the next sale starts 30/9 $15.49 40% off EDLP (Everyday Low Price) but that's more than the normal price in the supermarkets. Lol
Similarly they are selling Microgenics Vitamin K2 180mcg 30 Capsules $7.49, $7.50 Off EDLP . Next week $9.74 (40% of EDLP). So for 3 days the EDLP will exist to make it legal.
Thei fine print says: "The RRP against which any savings comparisons we make to the listed sale price for products displayed on this website is: the supplier's recommended retail price for the product, provided that this is a price at or above which at least 5% of Australian Pharmacy Transactions~ have occurred for that product within the previous 2 months; or if at least 5% of Australian Pharmacy Transactions~ for that product in the previous two months did not occur at or above the supplier's recommended retail price, the RRP will be the price at or above which at least 5% of Australian Pharmacy Transactions~ occurred within the last 2 months."
TLDR: Chemist Warehouse is legal but clever with marketing around their prices. Always check with competitor normal pricing and sales even when CW is 50% off otherwise you won't be getting a bargain at all.
Thanks