With avalon chips you get about 6gh/BTC with burnin's boards (that's purely CHIP PRICE, board price is not calculated)

20chips on BBXX = 9gh/s (450 mhz OC)
20 chips = 1.5 btc AVALON price (not going to calcualte for group buys + shipping etc.)

The BF chip is 3gh/s  so the price per chip should be less than .5 btc to match the gh/btc value of avalon.

However, if you have a board with BF chips similar to the BBXX = 20 BF chips = 60 GH/s with consumption 50watts (0.85w/gh based on the info on BF's site)

Power consumption compared to the BBXX is half and hashing power is 6.66 times greater so the BF chips are 13 times more power efficient than avalon's meaning you can mine with profit at a 13 times higher difficulty compared to avalon chips.

If BF's chips can hash at more than 3gh/s with burnin's design that would just be extra incentive ...

Also, another advantage is the hash power density which is 10 times higher with BF chips = of real importance to people who are looking to own larger amounts of hashing power and even more so if you are going to host your devices at a data center that charges based on rackspace used.

And in the end, if there's enough interest and burnin gets enough preorders (though the mention of preorder by him made me cringe) he can decide if it is worth his time to work on design for BF chips or just refund everybody.