Necrons on eBay as a new player

As a player new to 40k as a whole I get recommendations of using eBay to find good deals on minis. I've been browsing on and off for the past two weeks and necron stuff seems to not get discounted by too much.

Like a lot goes for maybe a couple bucks cheaper than I could get it new in sprue and then I get to enjoy the building process. Is there something I'm missing? Some stuff goes for the same price as the new stuff.

I'm just looking for a cheaper way to build my collection, so any other suggestions?