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!
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.