Any hotel gift shop will be high. GN and Circa probably higher. Any free standing store will be less, but not as low as Coast locations, Lee's etc.
Got two small bottles at the abc as I got there before it closed plaza had some wine and maybe booze one th8ng to note, was told I could not bring in my pop from Walgreens into Circa and I asked them even if I am staying here? After showing my room key, which they said was cool looking and have not seen them yet, they let me bring in my pop and booze with no fuss
Downtown, I can't think of any place that is a better value than ABC. Now, downtown bars tend to have really strong pours, but you are paying bar prices. The reality is that Walgreens downtown doesn't sell booze. As far as I know, only ABC sells liquor on Fremont St. A couple gift shops do sell beer, though, but the prices aren't all that different.
Southpoint has a lovely liquor store in the casino. Stop by, grab your booze and a bowl of clam choweder and then get out of my way ;-)
But isn't there a Lee's liquor store along the way to SP? I kind of remember seeing one when I was driving to SP. Although not sure how the prices at that place is.
There is one on the east side of LV Blvd north of SP. I've stopped there a few times. If SP has what you want, I'd just buy it there. Prices are close enough to Lee's that the effort of pulling in, going in and out etc. isn't worth it to me.