A year ago — even a couple of months ago — a Michael Jackson tribute band would have seemed an iffy, even laughable, proposition.

Now, of course, the post-mortem Michael Jackson market is the only economic sector that’s booming. A month after his untimely death, the singer’s stock has never been higher: Fans have bought 3 million Jackson albums since he died on June 25, and Jackson has six of the nation’s ten best-selling CDs on the national Billboard chart. Opportunism is rampant.

Business has never been better for Who’s Bad: The Ultimate Michael Jackson Tribute Band, and venues that snubbed the band are begging it for bookings. The band plays the House of Blues at Mandalay Bay on Wednesday. But the group has mixed emotions about its hard-won windfall.

“It’s sad that it had to happen this way for people to care,” says Vamsi Tadepalli, 28, who describes the past month as a “whirlwind” for him and the band he founded. He’s on the phone from his home in North Carolina, talking to a reporter while washing dishes.

He won’t be home again until November.

“I thought we were pretty busy last year,” says Tadepalli, noting that Who’s Bad played 150 shows across the country — counting travel days, that’s a full year for any band.

But there were certain places, he says, that wouldn’t give him the time of day.

“They were like, ‘Eh, Michael Jackson? I don’t know ...’ And now they’re the ones calling us.”

Tadepalli says the six-man group from North Carolina kept the faith during Jackson’s past decade, which was shadowed by controversy and contempt.

“We were out there during (Jackson’s) lowest level of popularity,” he says, noting that he put the band together in 2003.

In 2004, Jackson pleaded not guilty after a grand jury indictment on child molestation charges. (He was later acquitted.) Promoters were leery of booking a Jackson tribute band. People would scrawl things like “Don’t bring your kids” on tour posters.

“During that time, I took pride in it more than ever,” says Tadepalli, a University of North Carolina jazz performance major who assembled the group with fellow students. “It was like, ‘Look, I’m here about the music, and you guys can say whatever you want about the man.’ ”

“You guys,” he says, “being the media.”

The craziness started as soon as Jackson’s death was announced on a Thursday afternoon in June. Who’s Bad had been booked at Washington, D.C.’s 9:30 Club since March, and its half-sold Friday night show might have been just another copycat gig.

Then Jackson died. The remaining 600 tickets vanished in 90 minutes. A second show was added and that sold out, too. As Who’s Bad took the stage, Dan Zak wrote in The Washington Post, the band’s performance “turned into a media event, a center for emotional triage, a resurrection of sorts.”

“Some people who come to see us don’t even like Michael Jackson,” says Tadepalli, who plays sax and sings in the band (Joseph Bell and Taalib York rotate Jackson vocal duties.) “They get dragged by their friend or whatever. You can spot them in the crowd — they’ll be standing in the crowd, arms crossed, just looking at us like they’re not having a good time.

“And by the end of the show, their hands are up in the air, they’re screaming. Then they come up and say ‘Man, I don’t even like Michael Jackson, but you guys are awesome.’ And I’m like, ‘OK, I appreciate that, but if you think that we’re awesome and you don’t like Michael Jackson, you haven’t checked out Michael Jackson.’ ”

Tadepalli never had the chance to meet Jackson.

“It’s not like we’re mourning his death — we’re celebrating his life,” he says. “If anything has changed, it’s that we have a greater responsibility to go out there and play more shows. If people want to hear (Jackson’s music) more now, we’re gonna go out there and play it for ’em. That’s why we started the group.”