Material - Carnet de Passage en Douane

In some nations the vehicle needs the Passport, of course it is not called Passport but can be considered something similar. It is the warranty for the visited nation that you will not sell your vehicle. In Italy the ACI makes it with 250€ and a Fidejussione Assicurativa (because the fidejussione bancaria is never sold). If you are ACI user then the cost will be 150€. The ACI website explain it very well (italian language) and I think you shall ask your national vehicles registry  how to make it in case you live abroad.

The fidejussione assicurativa has a fixed formula P = TM x D  where 
P - is the cost
T -  is the interest ratio (0.2%-5%)
M -  is the amount to guarantee
D -  is the period in year.

So now for our project we could end up with a vehicle valued 35k euro, quite old, we'll stay abroad 2 years and I would set the maximum ration (5%).
P = 0.05 x 105.000 x 2 = 10.500€ (quite a bit). 
This website made an offer very interesting 900€ in total (circa 0.45%) and there are also website like assicurazioni-polizze which can help you to find the best price for your case.