Tanya assumes the price of tomatoes is the same across the whole city today — same day, same city

Why

Tanya is imagining one fixed price stamped on tomatoes across the city, but a price is set separately by each seller, and several things pull it in different directions on the very same day. Where the shop is matters — a shop in a wealthy neighbourhood often charges more than a stall in a crowded market or the wholesale mandi. How fresh the stock is matters — a seller with tomatoes about to spoil will drop the price to clear them before the day ends. And in many markets the buyer can bargain, so two people can walk away from the same cart having paid different amounts. Test it: check the price of tomatoes at the wholesale mandi, a busy street market, and an air-conditioned store on the same afternoon — they are usually noticeably different. Her friend is right: same city and same day, the price still varies with locality, freshness, and bargaining — there is no single citywide price.