@SheriGR my Sims still have all their stuff in their inventories. I did not see any differences in bills when they have it or not. But I need to check it out more thoroughly. Like I stated, I managed to graft a branch of the money tree onto an garlic plant, that my sims also grow indoors. Any time they harvest and collect it, instead of selling it, the bills stay the same.
As a matter of fact many of my households need to buy safes to stash the surplus they gain by collecting the interest on their wealth. It can go up to 500.000 per Sim per week.
The plot taxes that came with Eco Living are a different order. In my experience this tax relates to the Eco friendliness of the house, the plot and the household goods.
Having electric lights instead of candles causes the tax to increase. As does televisions, computers etc. You need to make the electric equipment more energy sufficient, the toilets, showers and baths safe more water etc. These actions also lower the plot taxes. Than of course you should watch out not to use the more industrious materials. In the build mode you will see if these materials will heighten or lower the ecological footprint of the plot. More industrious materials tend to give a surge in plot taxes.
So all in all household bills and taxes combined make up for the end bill that each household needs to pay.
When your household does it economically and ecologically right it will receive refunds on the end bill.