The biggest bets I've seen were on JD... 7000+ BTC bets. Several times. (Well, it went up to 7000+ from around 2000+)
Was 7000 BTC a one time bet?
Yes it was. It looked like 2000, 3000, 4000, 5000, 6000, 7000. ... It's not 1 BTC done 7000 times, but several 2000 to 7000 BTC bets a few times.