Kirkland brand liquor, in general, is unbeatable from a price-to-quality standpoint. I haven't had the single malt, but I can vouch for their single barrel bourbon, French Vodka, silver tequila, spiced rum, and silver rum. I don't do gin, but wifey says good things about the Kirkland brand version of that too.
I'm unlikely to buy a Kirkland putter as my 7 year old $70 Cleveland mallet is still the best club in my bag, but if Costco thinks it's worth $150, and if it mirrors the typical ratio of "how much the Kirkland golf product costs compared to a comparable quality offering from one of the big OEMs," then it'll be about as good as a $350 putter from another manufacturer. I'll never forget the original Kirkland ball... it smelled like pure gasoline and performed as well as any ball I've played.