You can make Key West vacation as expensive as you want, or make it affordable. Flights and accommodation will be pricey if you are visiting in the peak seasons, so if you visit during off season it will be better for the wallet. City sightseeing doesn’t have to be expensive, you can walk to various attractions, and use one tour (like the Trolley tour). Eat in casual restaurants. For your second day, choose 1-2 water activities (prices start at $50 USD) or just hang out at one of the public beaches to save money.