I`ll offer 4 BTC.
The price your given, is based on rising difficulties and other machines being added everyday to the network with the Terra Hash.
I can go on being more detailed, but there are existing forum posts about everything.
Prices on BFL, are deflated based on more requirements for performance. Anyone mining needs a minimum of 3-4 singles.
I'll sell you (2) Avalon 60GH mini's for 4.5btc/ea shipped FREE domestically east of the mississippi. PM me if interested.