asic miners prices

[thresher]

Who is pricing these things?
The price for machines seems to go down hundreds every week. 
What are these companies spending on them that a falcon miner could be 2k two weeks ago and 850 this week?
Also they have machines with similar specs from the same retailer with 2k in price difference  (silverfish and falcons)
I realize they are still not priced at roi (in general), but it is like they just pull prices out of a hat for these things.