Michael would have been richER!!!!!

Michael Jackson could have raked in as much as $1.5 billion had he lived ... at least that's what an entertainment money man told jurors today in MJ's wrongful death case.

Accounting guru Arthur Erk testified ... Jackson could have earned minimum $1.1 billion if he performed a worldwide concert and showcased his music in Las Vegas.  And Erk felt if ticket prices were high enough, the figure would soar to $1.5 bil by the time Michael turned 65.

There are a couple of problems.  First, MJ never planned a worldwide tour.  The "This Is It" tour was limited to London.  Second, the family is seeking more than $40 billion.

Another interesting thing ... Erk said he deducted what he felt Jackson would have spent between age 50 and age 65, when he hypothetically would have retired -- $134 million.