Bills are too high with expensive objects

I'm not aware of any objects that are unlinked from the taxes, but you might be able to make a custom tuning for your sculptures and add a custom state that at least increases this bills statistic: 235316<!--statistic_BBGameplayEffects_DecreaseBills-->. Wouldn't exactly solve it, just offset it like it does with the tag (but obviously make the number higher). The Eco Living items out there are the closest you get to examples of how it works, you'd be looking for lot_statistic_modifiers. Here's one object tuning as an example: object_PowerGenerator_GEN