DIANA Ross and Joni Mitchell may be as different musically as night and day, but when it comes to diva-esque behavior they can both belt it out.

While such A-list entertainers as Bruce Springsteen and Tina Turner are asking for $67 and $150 (respectively) for their summer tours' top tickets - if you can even get them - Ross's "Return to Love" Supremes "reunion" tour seats are maxing out at an astounding $250 a pop. But foxnews.com's Roger Friedman reports that fans of the mercurial superstar aren't biting.

As of last week, Ross's planned June 17 concert at Cleveland's Gund Arena had sold only 5,000 of its 14,000 seats. Similarly, Boston's FleetCenter had reportedly sold a scant 5,000 of its 19,600 tickets. And according to a spokesman at Atlanta's Philips Arena - where Ross is scheduled to play June 22 - ticket sales there are going "slow."

Even in Ross's hometown Detroit, a source at the 17,000-capacity Palace says there are "plenty of tickets at all prices" available for her June 19 show. Insiders say that Ross fans are being put off by the fact that although her show is billed as a "Supremes reunion," neither original member Mary Wilson nor longtime Supremes substitute Cindy Birdsong is performing.

Ross, who is reportedly being paid $15 million (plus a percentage of the box-office take) for the tour, offered a measly $4 million to Wilson, and even more paltry $1 million to Birdsong.

"We're moving ahead, and sales have picked up," insists tour publicist Rick Gomes. "There are no plans to cancel any dates."

In a similar what-goes-around-comes-around situation, "Circle Game" warbler Joni Mitchell is taking a few hits from her acoustically-inclined colleague Ju dy Collins over not getting credit where it's due.

Collins, who bolstered Mitchell's career when her cover of Mitchell's "Both Sides Now" became a Grammy-winning 1968 hit, was inexplicably left out of the performer lineup for TNT's recent "All Star Tribute" to her folkie protegee. "No one called - not Joni, nor the producers," Collins told Friedman at Mitchell's Monday night Madison Square Garden concert. "And I made a bundle of money for her when I did 'Both Sides Now.'"

Asked to appraise Mitchell's shaky performance of standards off her new album, Collins commented, "Don't ask me about that."