The price is too high for your la 90 considering the difficulty goes up everyday even if you ship by 15th may and customers receive by 20th may it will take them 3 months to make the money back they paid for the miner let alone profit. I suggest a price drop as many sellers are selling this same item from http://www.innosilicon.com/  all around even on alibaba.com.

If you can re consider your price and guarantee a working item with the warranty as you explained I might be able to get many people to order this even a group buy.