Quote Discrepancies

Hello,

New to forex and have a question that might expose some ignorance . . . but what would account for quote discrepancies of the same pair between two different brokers?

For example, OptionsXpress quotes the 1:00 am (Eastern US) 30-min high for GBP/USD as 1.57340 and Oanda quotes the high for the same bar as 1.57320.

Any insight is greatly appreciated.

Brokers have different liquidity providers, so can sometimes have marginally different quotes.