The price of gold in London is fixed twice daily by members of the price fixing company, for exchange of contracts between those members. The fix becomes the definitive price price for the whole market at that time. Supply and demand do the rest until the next fix. Why can't the largest n (by hashrate?) miners fix the price of Bitcoin for exchange between themselves?
The fix price could be determined by a periodic (M1?) auction of one BTC between the miners and the transaction of one BTC between lowest seller and highest buyer would be written in the blockchain like any other, therefore all nodes on the network would know the official price. The market as a whole would adopt the official price, because arbitrage would occur between the miners fix and the various exchange prices. This would reduce dependency on one retail exchange as the primary price discovery mechanism.
I think there are enough early adopters who could always sell lower then a cartel
