If the report on the proposed acquisition or improvement shows that the estimated amount proposed to be assessed upon any parcel for the proposed acquisition or improvement will exceed one-half of the true value of the parcel as set forth in the report, or shows that the total estimated cost of the proposed improvement or acquisition, less any amount to be paid towards the cost from any source other than special assessments upon the parcels benefited by the acquisition or improvement, when added to the aggregate totals of all unpaid assessments and estimated assessments, as the totals are stated in the report, will exceed in total amount one-half of the true value of all the parcels proposed to be assessed, the proposed proceeding shall be abandoned or modified so that the amount to be specially assessed for the cost of the acquisition or improvement will be less than the limits hereby established, unless the excess of the cost and indebtedness over one-half of the true value shall be paid from some source other than by special assessment on the parcels, or unless the limitation is overruled.