It really comes down to their condition, a rusted out one with mouse damage is maybe worth 1000, a clean one (assuming these are non-runners, but have engine and tranny) with all the trim pieces and no major body damage could range from 10k-20k or more depending on the the rarity of the package and engine in them.
If they were running I'd say the lowest they would go for is 5k (mild rust). (I am basing this off my 59 Chev Apache and the equivalents that I have seen)