Bills are calculated at the same time each sim week and depending where your sim is effects the bill. So if your sim is on another lot (apart from their home lot) unfortunately the game calculates that lot as part of the bill percentage. So leaving any item in a sims personal inventory or home inventory will add to the bill amount.
The bill calculation error has been a round for a very long time, almost since the game launched actually. But, that being said, I like it as bills are far too low in TS4 anyway.
But
@oshizu , the game is so easy! You know it is! You're one of the better strategic players and anything that can add to the difficulty only adds to the enjoyment of a challenge. lol My first draft of this challenge involved leaving quite a few expensive items in the household inventory for the very reason of making bills more realistic!
And playing with a vamp initially increases the difficulty too. It's fun!
@reggikko you're a strategic player too. You'd find this challenge easy.
Dang it all, now you guys are making me desperate to play it, I wish that silly vet bug wasn't around. Grr!