Foreigners in Varanasi will often be overcharged by the shopkeepers. Remember that EVERYTHING should have a price tag on it -even / especially alcohol. If this is missing or scratched out, it is because they are trying to cheat you -either by removing the tag, or (worse-- because the booze is FAKE. Do NOT drink the alcohol if there is no price tag- fake alcohol kills thousands in India every year).
Do not say "well, it's just a couple dollars extra" --this might kill you. Do not think "this is a foreign brand, it must be good" --this might kill you. Beer in cans is safe, and often the small bottles of whiskey are safe (the counterfeiters tend to maximize profits by going for big bottles). Gin is often safe, so ask for gin (not vodka- most of the Absolut Vodka is fake).
There are possibly four honest stores: in SIGRA near the El Chiko bar; in LAHURBIR, in NAWABGANJ behind the Pilgrim's Book Store )near Durga Kund), and on the road to SAMNE GHAT, near Maheshnagar. You can trust these guys, their prices and products.
REGULAR CHEATS: in LANKA, near the Canara bank intersection; in SONARPURA, near the main road. These are most convenient for tourists, not coincidentally.