A lot depends on specific configuration. For example we have two different configurations of A332s in our fleet, one is configured in an all economy style with 340 seats and weighs 121.993kgs empty which comes out at 359kg and the other one has 19 business and 279 economy seats with an DOM of 122.232kg which equates to 410kgs per seat. Same basic aircraft, different weight. The difference between our 180 seat A320s and our 12/132 seat A320s might be even bigger, but i'm too lazy to look up the numbers.
Just for comparison: Dash 8 Q400, 76 seats, 18.472kg DOM, 243kg/seat.