I have a google sheet that I use to track prices on my favorite & WTB bottles, I try to update it every couple of months when I pop into a store. There an app called BoozeApp that I use as well, I find that's usually pretty accurate for initial ballpark numbers.
Not only store to store, but prices can vary based on time of year in the same store. I find that prices are often 15% to 25% higher during the holiday season (November through January) in some stores. Buy your holiday gift bottles now if you can!