alexey remember you have setup fees which don't change regardless of the size of the batch (factory-dependent), you have component handling and transportation fees, and you have "over-runs" on components. trays are say 900 per tray, if you buy 2,000 you have an over-run of 800. tape and reel is 2500 typically: if you buy 2,000 you have an over-run of 500, and it's just bad luck if you want 3,000. no, *nobody* will sell you part-reels: they get thrown away, storage and stock maintenance costs are not worth the effort.
then there is testing, handling, shipping, tax and more.
l.