High Profile Accounts Banned.

Those kind of transactions are not untraceable, and if the seller is transferring money at the duel arena then there's a pattern that develops where the seller risks way more than his opponent and never wins. Instead of blocking those kinds of uneven duels, it makes more sense to watch for that kind of unusual behavior and mark the account as one that needs to be looked at more closely.

The same goes with any other method of transferring wealth, and there's absolutely no reason why Jagex shouldn't already have a system in place for logging dramatic changes in wealth from trades, duels, drops, etc.