The estate of the late Perth mining billionaire Michael Wright is fighting a court decision awarding $25 million to his youngest daughter, arguing the $3 million he left her was enough.
Olivia Mead, from Mr Wright's relationship with Elizabeth Anne Mead, was aged 19 in 2015 when Master Craig Sanderson of the Supreme Court of Western Australia ruled her bequest should be increased more than eightfold.
Ms Mead's older half-sisters, Leonie Baldock and Alexandra Burt, were left most of their father's estate - about $400 million each.
Ms Mead's share was only going to be available when she reached 30 and clauses in the will included limiting her religious affiliation, which meant she could have ended up with nothing.
Jane Needham, representing estate executor David Lemon, told the full bench of the WA Court of Appeal on Thursday that $3 million was adequate for the proper maintenance of Ms Mead, who compiled a lavish wishlist to estimate her future requirements.
It included a $US1.2 million crystal-studded grand piano, a diamond-encrusted bass guitar, upkeep for her pet axolotl and provision for four children that she plans to have, and originally amounted to $20 million but was revised down to about $12.5 million.
Master Sanderson said Ms Mead had simply let her imagination run wild, the same way most teens would if asked to outline such needs, was not "a gold digger" and awarded her $5 million more than she had initially asked for.
But Ms Needham said Master Sanderson had in effect regarded the size of the estate as trumping any other factor he needed to consider and he erred in regarding his discretion unfettered.
- Rolf Harris granted bail on groping charges, to be released from jail
- 'Leave her alone': Schapelle Corby's sister pleads for privacy
She said it was wrong to award Ms Mead twice as much as what she ultimately sought after considering "some quite extraordinary items" - even in the revised wishlist - without accounting for her or her partner's future income.
Ms Needham cited Ms Mead's call for 20 pairs of $300 shoes every year for the next 75 years and Pilates lessons until she is aged 97.
Justice Michael Buss said he made no criticism of Ms Mead, but such items were "just silly".
He asked how the judges would evaluate what was proper in the circumstances, saying a reasonable house and income might be what was needed.
Ms Needham also said it wasn't appropriate to make the estate provide for Ms Mead's planned four children.
But the 21-year-old's lawyer Lindsay Ellison said there was nothing that couldn't be taken into account when assessing what a daughter from a wealthy family might need for the rest of her life.
"It is a large result but it's minimal compared to the size of the estate," Mr Ellison said.
There were also no competing claimants, he said, and the court could "go that extra bit further, and add some cheese and jam" rather than just the essentials of life.