The board of supervisors of a county may require registration and establish a schedule of annual registration fees to be paid by any person who acts as a wholesaler of fresh fruit and vegetables under any license required under Chapter 7 (commencing with Section 56101) of Division 20, and who maintains an office or salesroom or conducts that business in the county. The schedule shall be designed to pay not more than one-third of the costs of the county for the administration and enforcement of this division or any regulations adopted pursuant to this division. Any funds derived under this section shall be used only for the enforcement of wholesale inspections of fruits and vegetables pursuant to this division. The maximum fee that may be established pursuant to this section shall not exceed two hundred fifty dollars ($250).