The special assessments need not be imposed on different classes of business, as determined pursuant to section 50-2608, Idaho Code, on the same basis or the same rate:  Provided, however, that the special assessments imposed for the purpose of the acquisition, construction or maintenance of parking facilities for the benefit of the district shall be imposed on the basis of benefit determined by the legislative authority after giving consideration to the total cost to be recovered from the businesses upon which the special assessment is to be imposed, the total area within the boundaries of the business improvement district, the assessed value of the land and improvements within the district, the total business volume generated within the district and within each business, and such other factors as the legislative authority may find and determine to be a reasonable measure of such benefit.