Of all the one-of-a-kind Prince items to go up for sale since his death, Chris Moon's new offering might be the biggest surprise with the highest price tag.

The former Minneapolis studio owner, who helmed Prince's earliest demos, is selling his co-writing credit to Prince's 1978 debut single "Soft and Wet," and you don't have to be a record-label mogul or member of Prince's inner circle to buy it.

Over the weekend, Moon put his stake in the song up for auction on eBay with the "Buy It Now" price of $490,000. He is also taking bids for it — and offering free shipping, too.

"Co-own a Prince song with Prince!" Moon's online ad reads.

Reached by phone Monday morning at his home in Fort Meyers, Fla., Moon laughed about some of the particulars involved in the auction but confirmed it's 100 percent legitimate.

"It's very unusual, but it's completely real," he said. "Nobody has ever done anything like this before that I know of, so I understand why some people don't believe it."

Moon famously believed in Prince in 1976, when he handed over the keys to his Moon Sound Studio in south Minneapolis to the future Rock and Roll Hall of Famer, then still a student at Central High School.

Prince recorded his first demo recordings as a solo artist at Moon's place, including a handful of songs based on lyrics Moon himself had written. One of those songs was "Soft and Wet," which was used by Warner Bros. Records as the first single off Prince's 1978 debut album, "For You."

Four decades later, Moon said he has enjoyed his "relationship" with the song and "would now like to see someone else get the same enjoyment out of it."

"I'm nearing retirement age, so I'm selling off some of my assets," he said.

Selling rights to a song is a relatively common occurrence in the music business. Co-ownership of a song's publishing copyright results in revenue from album sales, digital streams, radio play and any TV or movie usage.

What's unusual about this particular sale is a) a very small percentage of Prince's songs have co-writing credits, and the rest are all in his name and b) the fact that it's being done via eBay.

"I've had very good luck with eBay in other business ventures," said Moon, who also owns a high-end audio gear company. But he also liked "the element of surprise" doing it as an eBay auction, and the idea that "it's really open to anyone," he said.

Mick Spence, an entertainment and copyright attorney at Hellmuth & Johnson in Minneapolis, was amused by Moon's chosen method of sale — "That's a first," he said — but otherwise believes everything else about the deal should be relatively routine.

"Just like you would check on a title before buying a house, you would want to check the paper trail on this and make sure everything is clean," said Spence. "But based on what he's advertising, it looks like [Moon's] rights are still in good standing."

Not-so-royal royalties

Of course, that doesn't necessarily mean it's a good investment. "Soft and Wet" barely cracked Billboard's top 100 chart when it came out, is far down the list of Prince's best-loved singles and was featured on one of his poorer-selling albums. Not to mention, royalty rates for songs have greatly decreased in recent years as digital streaming took over the record industry.

Moon said he made more money off the song thanks to MC Hammer's sampling of it than he did on the Prince version. The rapper used it as the basis for "She's Soft and Wet," a track on his 1990 blockbuster album "Please Hammer, Don't Hurt 'Em."

"Anyone who buys this probably shouldn't be doing it for financial purposes," Moon admitted. "It's more about owning one of the most unique collectibles ever related to Prince."

Moon owns several other pieces of the star's career, including those original demo recordings that landed Prince his Warner Bros. deal. Moon also owns the full rights to one unreleased song from that era, "Make It Through the Storm" — which he said Prince gave to him after failing to give him writing credit for another song on the "For You" album, "My Love Is Forever."

Perhaps most intriguing of all, Moon — who back then made his living recording jingles for Campbell-Mithun and other advertising agencies — owns what's probably the one and only commercial jingle that Prince ever recorded. He wouldn't name the company it was made for, but he said, "People would be very amused by it."

Moon hopes Prince fans are entertained by the "Soft and Wet" auction, too. He pointed out the fact that, aside from this one song credit, he was never formally paid for his work with the young Prince, but he added, "It's not about the money."

"I've had a lot of fun with this song over the years," he said. "Now, it's somebody else's turn."