After my wife passed away a couple of months ago (she was the motability customer) i enquired about purchasing the car we had on the scheme a toyota c-hr icon.
The price motability quoted was £18200 which is about the ave forecourt price for that model& mileage.
I was informed they give the car a check over before sale similar to an mot.
Only drawback is there is no guarantee/warranty from the moment of purchase, even 2nd hand dealers will offer 3 months.
I have also heard other prospective buyers have tracked their car through auction & in all cases the vehicle has sold for less than the price motability offered it to them+auction selling fees to be added to this.