How much does an elevator increase market value?

[Cheri Bumbera]

Possibly a question for appraisers - does anybody know how much an elevator should increase the value of a home? The only other access to the main floor of the home is a 17 step staircase. It is located in the hill country of Texas where many homes are built on the side of hills and stairs are the only access to the home. The cost to install was $55,000. Thanks in advance.