Any assessment levied by the commission, pursuant to this chapter, is a personal debt of every person so assessed and is due and payable to the commission within 30 days after the date the vintner deducts the assessment from the amounts paid by the vintner to the producer. The vintner first acquiring the grapes being assessed shall deduct the assessments from amounts paid by the vintner to the producer and shall be a trustee of the funds until they are paid to the commission. The vintner responsible for deducting the assessment may deduct and retain an amount not in excess of that reasonably necessary to cover the actual cost of services provided by the vintner, as determined by the commission. Failure of a vintner to collect the assessment from a producer shall not exempt the vintner from liability nor relieve the producer of the obligation to pay the assessment.