After further thinking, this is a very interesting topic: People might give up those credits instead of sell them cheap
Suppose that there are 2000 chip credits and there are only 1000 chip purchasing order, if every one go to market place and compete to lower the price to sell their chip credit, they will eventually reach a very low price for each chip credit, almost 0. (If you do not accept that price, your chip credit will not get sold and become useless, so from a pure profit point of view, everything above 0 is acceptable)
But, if they reach a consensus automatically that they will not lower the price below a certain threashold, eventually they would still sell 1000 chip credits at a much higher price (for example $12.5, for chip buyers any amount of discount is good), so the average chip selling price would be much higher than previous case, avoid a "race to the bottom" price war
The question then is... would you buy bfl Asic chips when the GH there costs 62.5% of the avalon asic chips that deliver in 2/3 of the time (difficulty) and nearly the miners are ready? I think when bfl didnt catch buyers with 25% discount it will be hard to sell the credits high.
That's what I mean, only a few people will purchase the BFL chips, thus the demand is less than supply
But anyway, from a long term perspective, BFL chips will still be profitable when ASICminer and Avalon's chip can not make back the electricity cost, as long as it's profitable, the size of the mining farm can be continuously expanded