Haven't the owners already made a solid offer?
No, they have not. The owners made an initial economic proposal during August discussions with the MLBPA, but it was not a compelling offer from the players' standpoint. According to Evan Drellich and Ken Rosenthal of The Athletic, the league's proposal would "lower the first luxury-tax threshold in the sport to $180 million" while upping the overage penalty. Additionally, the league would institute a "salary minimum of $100 million," with the "money collected from teams paying tax" going to certain teams to help them meet the minimum.
On the surface, this would seem to address the ongoing tanking problem, in which rebuilding teams in essence lose on purpose -- an exercise abetted by low payrolls. However, the luxury tax, which already functions as a soft cap, hardens under this proposal. The bottom line is that in terms of the players' share of revenues, this constitutes a loss for them measured in the hundreds of millions of dollars. So, no, it's not a serious offer.