It depends on the value of the lot including the Sims inventory. I tested it. I often play rags to riches. In the beginning my Sims have no money and no furniture. The bill increases with every single piece you add. It makes no sense getting a higher bill when the Sim lives off the grid in a tent and only has some plants and a market table to earn money. He has no toilet, only a bush, and collects water from the river.
Higher bills for only having a better bed or table is not realistic and doesn't make sense.