Where is the authoritative source for the Bitcoin price?

Well, there isn't one.

So differences in price for bitcoin occur at different marketplaces ... just as the price of a tomato is different at different grocery markets.

There are various methods that attempt to consider various marketplaces to come up with a more sane, commonly available price.

For instance, Coindesk has their "Bitcoin Price Index", which they suggest the symbol XBP, and the method it is calculated is shown here:

CoinDesks's BPI is used by a number of financial media (e.g., Bloomberg/WJS) and trading products.

There's also the BraveNewCoin's BItcoin Liquid Index (BLX):

The BLX is used by NASDAQ.

The CME has its own "prices", BRR (Bitcoin Reference Rate) -- the "closing price" used for daily settlements, and BRTI (Bitcoin Real-time Index):

MVIS:

TradeBlock (XBX):

BitcoinAverage:

CoinTelegraph:

CoinMarketCap:

Messari OnChainFX:

Nomics:

Winkdex:

NYSE (NYXBT):

Others:

Charts:

Basket / Altcoin indexes:

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