Mark Gray, who had financially supported Ms Price and her family, told the Supreme Court he believed Ms Price planned to give her accused killer, her on-off boyfriend Ricardo Barbaro, some of that money.
"I assume that the boyfriend will be needing it and no doubt she will give it to him," he said in a text read to court on Tuesday.
Ms Price told him she needed the money to open a salon, but Mr Gray told others, including her mother, he thought this was a "joke" in text messages.
Mr Gray said he thought Ms Price's demand for $100,000 represented "quite an extraordinary change in behaviour".
He paid Ms Price $25,000 and said he planned to try and get more money to pay her and Barbaro again in September.
Barbaro, 36, has pleaded not guilty to murder and is facing a jury trial over the death of Ms Price, 26, whose body was found by police in her South Melbourne apartment on May 4, 2020.
Prosecutors allege she was fatally stabbed by Barbaro in the early hours of April 29 before he went on the run.
Mr Gray, who owns and operates brothels in Melbourne and Sydney, met Ms Price in 2017 at Melbourne strip club The Men's Gallery, where she worked as an exotic dancer.
He helped find accommodation for Ms Price and her young son, writing references and paying more than $150,000 over about three years towards her rent, which included luxury CBD apartments.
Barbaro's barrister Rishi Nathwani referred to Mr Gray as Ms Price's "sugar daddy" as he had spent thousands of dollars supporting Ms Price and members of her family, but Mr Gray denied this.
"I'm not a sugar daddy ... Anyone who comes to this courtroom will tell you the same," Mr Gray said.
After giving evidence, Mr Gray, disguised with an umbrella and sunglasses, was escorted out of the court via a side door by a security guard to avoid media.
He will return to the witness stand on Wednesday, when Barbaro's trial continues.
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