It's a given that the MiLB salaries are paid by the club. For the non-players working in MiLB, it's a business model issue.
Roughly 300 MiLB players in an organization? Let's use that number, and an average monthly salary of $1700. $500K in salary per month to carry MiLB players in the budget.
Let's say that miraculously there's a new wage scale based on the forthcoming $15/hour minimum wage, and it's for 8 hours per day, working 28 days each month. Works out to be roughly $3400 average monthly salary. Double the current pay.
Can the club go from $3MM in MiLB player salary to $6MM? Is that a budget killer? Should a club cover that additional $3MM per year to prevent lawsuits, prevent dopey legislation that can backfire, prevent counter-legislation, and maintain federal antitrust status? An additional $3MM/year is a good deal.