A few examples from high-density European charter flying in the 90s:
B757-200 APS weight 59750kg, 235 seats, 254kg/seat
B767-200 APS weight 83200kg, 274 seats, 304kg/seat
B767-300 APS weight 91500kg, 344 seats, 266kg/seat
NB: APS weight includes crew and galley stores, for which I no longer have figures