Children do cost quite a bit to raise. I guess maybe Usagi and co. could stick the disguise pen in her hand, have her say things like School uniform, undress her but keep the clothes, and repeat until they have enough, and they did treat her to things like ice cream on enough instances, but you need more food than that. At least some bags of cat food, cat litter, and sleeping with Minako or Usagi isn´t too bad for Artemis and Luna, Usagi and Minako might even have enough money in their own right to pay for it themselves (although probably not pet insurance).
I guess the hypnosis Chibiusa used on the Tsukinos made them more than happy to dole out a few hundred thousand yen. I´m thinking that one of them came back with some of Neo-Queen Serenity´s jewels she gave to be sold off or Ami and Chibiusa hypnotized some bureaucrat to issue a tax credit to Kenji and Ikkuko.
I guess the hypnosis Chibiusa used on the Tsukinos made them more than happy to dole out a few hundred thousand yen. I´m thinking that one of them came back with some of Neo-Queen Serenity´s jewels she gave to be sold off or Ami and Chibiusa hypnotized some bureaucrat to issue a tax credit to Kenji and Ikkuko.