That helps only to a point. There are effectively three types of vehicle theft: to resell the car (whole or in parts), to use it for crime acts (robberies etc), or to joyride it. Category n.2 explicitly targets cheap cars, easy to steal but also easy to go unnoticed on the streets afterwards.
(1) having a cheap car stolen incurs a smaller loss than having an expensive car stolen; and
(2) the pool of cheap cars is larger, reducing the probability of a given car getting stolen (unless the "demand", so to speak, is also higher?)
Overall, it seems that the expected loss (actual loss times the probability) should be quite a bit lower for cheap cars than for expensive cars.
Having said that, if one has enough money to buy an expensive car, they presumably have enough money to insure it from theft, rendering this whole line of argument moot (they just pay higher premia and spread the risk across a population of car owners)...
