1) If you say explicitly that the minis have problems, then the customer knows what he is getting into.
2) You also adding a big discount, so there is incentive to buy.
3) If you want to be even nicer, you can add pictures or description of the damage/problem. This is extra, first two points are already good enough most of the time, and pictures/descriptions take a lot of time to do it for each mini. Maybe make groups, i.e 1 = broken part, 2 = missing a part, 3 = bubbles, etc. 
War Wagon (1, 2, 3, 4)
*4 = no existent