It all depends on a few factors your location, manufacturer if you have just a straight staircase or one that curves or has another landing. most of them just plug into a wall outlet. I new two people that had one. I know someone that might have one to give away that lives in New Jersey. I don't know your location.
Hi there!
Well, before buying the device it is advised to research well, on the available models according to ones requirements and the desired functions. The average cost may vary from 2000-5000$, while those at the higher end with additional functions may cost 1000-3000$ extra.
Hope this helps.
Take care!