However, in a new filing obtained by People, Katherine maintains that the estate, valued at $1.5 billion, can afford to pay her legal fees and should do so.
Katherine receives an allowance from a sub-trust created by Michael's will, but is not a direct beneficiary of her late son's actual estate.
She apparently racked up about half a million dollars worth of legal fees in her still pending appeal against the Sony sale.
In Bigi's objection, his lawyers contended that it was unhelpful to the estate for it to bankroll Katherine's appeal, which in their view is unlikely to succeed anyway.
'It is readily apparent that a reversal on appeal would be an extreme longshot,' read part of the objection, which was filed March 18.
'Given those odds, Bigi decided not to waste his resources to participate in an appeal. Nonetheless, Katherine has decided to appeal this court’s ruling. That decision is not for the benefit of the heirs.'
However, Bigi left the door open to covering 'reasonable attorney fees and costs' for the process of presenting 'essential evidence' during her first objection to the sale.
Katherine was not mollified, firing back with a legal response on March 20 in which she denounced the estate's purported tightness with money.
Her filing said in part that 'it seems clear to [Katherine] that the Executors are holding all of the assets in the Estate in order to keep control over them, and to avoid the more liberal distribution requirements of the Trust.'
She held that 'the Executors cannot in good faith contend that the Estate does not have sufficient available funds to allow the Trust to make the requested payment.'
In her view, the estate could pay for her legal expenditures without incurring any 'loss to creditors or injury to the estate or any interested person.'
Katherine's filing added: 'This vastly exceeds its potential liabilities, and leaves hundreds of millions of dollars available for the remainder beneficiaries.'
Michael died at the age of 50 in 2009 from a cardiac arrest he suffered after having Propofol administered as a sleep aid.
He left all of his money to his three children and to Katherine, who assumed custody of Prince, Paris, and Blanket, all of whom were underage when Michael died.