Whenever a county, or other political subdivision of the state, except incorporated cities and towns, shall have, out of public funds, purchased or constructed across any navigable stream any bridge that forms a segment or part of the state road system or any easement thereon, then the state highways and transportation commission, at any such time or times as the road funds will justify without interfering with other state road construction or maintenance, may construct and build such roads in such county or other political subdivision as the county commission of such county or in which such political subdivision is situate may direct; the cost of which roads shall be equal to the value to the state at the time taken over of the portion of such bridge entirely within the state of Missouri, not exceeding in any case the amount expended by such county or other political subdivision in the acquisition of such bridge; provided, however, that any county or other political subdivision except incorporated cities and towns may elect to receive such reimbursement from the state highways and transportation commission in cash.