As of my last knowledge update in September 2021, the cost of an Alcatraz tour varied depending on the type of tour you were interested in. The prices might have changed since then, so I recommend checking the official Alcatraz Island website or contacting their visitor center for the most up-to-date information. However, as of 2021:

1. Alcatraz Day Tour: This was the most popular option. It included round-trip ferry transportation to the island and the audio-guided Cellhouse Tour. In 2021, the cost was around $39.90 for adults (ages 18-61), $37.65 for seniors (ages 62+), and $24.40 for children (ages 5-11).

2. Alcatraz Night Tour: This option provided a unique experience of visiting the island in the evening. It included a guided tour, a boat cruise around the island, and special programs. In 2021, the cost was around $47.30 for adults, $44.05 for seniors, and $30.80 for children.

3. Alcatraz Behind-the-Scenes Tour: This tour offered a more in-depth experience, including additional areas of the island and access to areas not included in the regular tours. The cost was higher, typically around $93.90 per person.

4. Alcatraz Combination Tours: These were packages that combined the Alcatraz tour with other attractions in the area, such as a city bus tour or a visit to other San Francisco landmarks.

Remember that prices can change over time, so it's essential to verify the current prices and availability before making any plans. You can visit the official Alcatraz Island website or contact their visitor center for the most accurate and up-to-date information on tour costs and options.