DFAing Gallegos was not about saving cash. The Cardinals will save $0 unless they can find someone willing to trade for him and to assume the rest of his salary this year.
Other clubs can just wait until he clears waivers and sign him for the pro-rated minimum.
As for next year, the Cardinals ownership has been using the same lines since the pandemic. They are seeking public funding for their ballpark renovations.
Team payroll will probably decline next year, because team profits declined this year (lower announced attendance, even fewer actually in the stands).