Most often the cost of something is directly correlated to the quality of the product - say a Lexus for example.
Not necessarily true with all wines and something else we're found of around here.
Black Box wines are sold in most every grocery store in DFW. The Merlot small box, which holds roughly two glasses of wine, is a very well balanced smooth Merlot and in a blind taste test, you'd think it would cost around $20 a bottle - NADDA ! - under $4.00 EVERYWHERE! Simple good choice in a casual dinner for two.
The 2015 Colombia Crest Cabernet Sauvignon is rated a 91 by Wine Enthusiast Magazine. It's sold primarily at Costco for $6.97 a bottle and it's one of the best bottles of Cab I've ever tasted. I have several bottles rated higher at over twice the cost that can't compare to this wine.
If you're a red wine connoisseur, I think you'd agree that many of the reds coming out of Washington state are exceeding the quality of the Napa and Sonoma wines. I had a sommmelier giving a class on reds at Robert Mondavi say those exact words to me a short while back.
A trend I've noticed lately is a bunch of red blends that are super and these are coming from around the globe - South America (Chili), Argentina, California,France, Washington, & Spain.
For me, I purchase easily 90% of the wine I drink from Costco because many of their wines are rated and you don't have to guess on a new one as if it's going to be pored down the drain or consumed with a nice gourmet snack or thick grilled steak.