If you go on https://bitcoinaverage.com and look at the
Global Price versus Currency Markets
you’ll see the exact same difference.
Bisq uses the Currency Markets price.
Global price in BTC Average is calculated from USD and converted to local currency. We use local price where appropiate as that reflects more the real price in that currency. E.g. EUR price is composed from major EUR exchanges… The global price can often be different to local prices. Arbitrage trading in BTC to lower those differences is still under-developed.
Prices are updated every minute. When hoovering over the price you see the latest update.