I believe the rationale for Motability asking a high price from a customer to buy their vehicle at lease end, is to deter the customer from actually doing so.
The reason? In most cases, Motability would then have lost a profitable lease customer (unless the vehicle was being bought as a second vehicle, or for someone else, which would only apply in very few cases).
Leasing customers are profitable to Motability and the dealerships, likewise the resale through MFL Direct. If the customer buys their vehicle and goes ‘off scheme’ it is a net loss to Motability and the dealership network, who all want the customer to lease another scheme vehicle.
Hence Motability asking ‘top book’ or even over ‘top book’ price for the vehicle.
Business is, after all, business!