.
The only way you get anything back when you hand the car back is if the actual value is higher than the guaranteed future value.
Deposit can be misleading as a term, think of it as a down payment. The larger the deposit the smaller the repayments (assuming other variables such as APR etc. remain unchanged).
It's a bit more complex than that. No wonder people are confused by PCP's!
Best I can. If you wait till the end of the, say, three year contract then you are partly right in that if the part ex value of the car is higher than the GFV they will give you the part ex value IF YOU BUY ANOTHER CAR.
If you don't want to buy another car from them and just want to hand the car back you will get their price for cash (if they want to buy) or the GFV whichever is the higher.
Or you can sell to other dealers -'the trade' - at trade value or can sell privately.
BUT and this is important- if you sell early, say to buy another Mercedes you can ask for the 'redemption value'. Then ask the dealer what he will give for the car in part exchange. If his figure is higher than the Redemption value you pay off the car and keep the surplus towards your new car. If the part ex is less, you need to pay the balance. He offers 10k, redemption is 12k so you need to find 2k. That is what you have lost on top of your payments and deposit if you settle early.
Thirdly, if you don't want to buy another car, you will have to sell for cash and pay the redemption value, or just pay the redemption value if no better cash value is available.
Fourthly, if you settle after more than half the total payments have been made, (check definition of half in your T's and C's) then in theory you can walk away and pay nothing. But some think that will harm your reputation/ chance of further loans etc. Personally I would never advocate walking away from a legal contract entered into on both sides in good faith, except in extreme circumstances.