I like the idea of Dark Elves bringin slaves to the battlefield as cannon fodder, even though it's a bit against the fluff. They see slaves more of a currency and too valuable to waste in combat... That's why it's sort of fits in. I play them with regular Dark Elf warrior stats so with shields they cost 8pts, compare that to skaven slaves at 2ps each... So they are expensive in a way which is just right. I put the first rank on a regiment base so I could link 4 slaves together with chains. The rest have chains too but they just hand down or links their hands to their necks.