It is not a scam, more likely the bitcoin/USD price drop is due to Avalon's bitcoin payment processor (Bitpay?) converting (selling) thousands of bitcoins to fiat currency as people are ordering the ASIC chips from Avalon. With the wide-swing, I wouldn't want to hold on to too many bitcoins for too long if I am Avalon, better to take profit in real currency now. They can always generate more shiny new bitcoins while they are testing the Avalon machines.
It's funny that draw the preorders just in the biggest drop in the price of bitcoin, and now here you take bitcoins to sell the product two months waiting for a raise ... I see quite scam.