WAV purchase cost at end of lease

[mattross]

My converted VW Caddy is coming up to the end of its 5-year WAV lease. Motability have agreed to extend that by an additional 2 years. After that I will be intending on buying it, as it's got a fortune invested in adaptions not provided by Motability (the bulk of which is a SpaceDrive 4-way joystick). Does anyone know how they calculate the final purchase price? Will it be broadly equal to the retail sell value at the time I buy it? Or do they reduce it at all according to the advance fee I paid (£15,000)?

At this stage I have two years to worry about the cost, but an idea of the damage now will help me budget for it. Of course the other thing that worries me is the longevity of the SpaceDrive system. Can I expect that to last 15 years or more (with annual servicing), or am I dreaming?

[Burgerman]

Does anyone know how they calculate the final purchase price?

Basically it is whay the expected price when you leased it was. If you have loads of adaptations that can but doesnt usually make much difference to the book value.