It is supremely appropriate for Far Cry 2 that a dead king’s son – for whom it should be noted you have just committed an act of regicide – chooses to repay you with a gift that is completely and utterly disposable. A four wheel drive, even one with gold rims, is functionally no different to any other of the same type and is guaranteed to become a hindrance at some point, at which it will be unceremoniously left at the side of the road. The same type can be found scattered around several places and despite its tank-like appearance acts nothing like. Much more likely is that it endows you with a false sense of security and gets you killed.
And this one mission is just another little detail to contribute to the overall theme of disposability – disposability of life, vehicles, weapons, health. Nothing lasts, everything decays; No one gets out alive. The things that are indispensible to you are only those that were here before you arrived – the safe houses; the land itself – and the occasional things your buddies add to them.
Guns, while not biodegradable as pointed out so poignantly by The Jackal in one of his many tapes, are in fact the ultimate height of disposability. You aren’t even presented with the choice of keeping them – they rust, get jammed, and eventually self-destruct like a Mission Impossible style mission. “This gun will self-destruct after three more jams.” Life-safing syrettes of drugs are one shot, and never re-filled; they’re simply flung away to be replaced by a new handful later.
Disposability is built into the human aspects of the world.