Donald Trump claims he is worth billions, but another wealthy businessman has his doubts.

The presumptive Republican presidential nominee's real estate success has not necessarily yielded the wealth Trump claims, entrepreneur Mark Cuban told WABC's "The Bernie and Sid Show" on Wednesday. He added that Trump is "not transparent enough for us to really know."

"I'm not so sure Donald knows what he's not good at. What he's done well is put his name on big buildings, right? He appears to have done well putting his name through a licensing arrangement on hotels and buildings. He's good at that. Now, whether or not that's made him a billionaire, I don't know," the Dallas Mavericks owner and "Shark Tank" investor said.

Earlier this month, Trump claimed a net worth of more than $10 billion. He said his 2015 income topped $550 million.

Some experts have disputed his net worth, and Trump has been criticized for not yet releasing his tax returns. Presidential nominees typically do so.

Trump has touted his wealth and business acumen throughout the election as evidence of his viability. He repeatedly boasted about his ability to loan his campaign most of its funds, though he is now raising money with the Republican Party for the general election.

Cuban acknowledged Trump's talent in real estate but questioned some of his other decisions. He said products like branded water bottles and steak reflect "desperation."

Cuban said he asked Trump, "Are you that desperate for money?"

The Trump campaign and Trump Organization did not immediately respond to requests for comment.

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