That doesn't seem uncommon, there are so many times I see single items go for what a completed or nearly completed item will go for. I guess some folks just want to get "their" peice done, they soley focus on the missing parts
I completed a couple AT-ATs just by watching and buying imcomplete units and cheap prices, now I have a mini ATAT junkyard but it's all good.
This isn't just the case with toys, I run into this all the time with my car projects, A good example is I saw a 1971 GS last year for parts, the car was complete with the desirable GS hood and it was $1000 bucks, then you can find just a GS hood on ebay for 500-750 alone. It's worse when you hit the "rare" years or models just like SW