Notwithstanding any other provision of law, in any county having a population of more than 90,000 which adjoins three or more cities of the first class the redevelopment and housing authority of the county may, from funds of the authority and with the approval of the governing body of the county, pay each such commissioner not exceeding $25 for each day or part thereof spent in discharge of his duties as such commissioner; provided that no such commissioner or his successor shall be paid more than $300 in any year.