Money isn't the only cost in this scenario. If you are buying an aircraft to do serious, reliable travelling then the old twin may spend far too much time in the shop. Something new, with guaranteed maintenance parameters, would be a better bet.
In countries that allow such 'stupidities' new(er) singles, particularly single turbines, are taking over serious flying from old piston twins. Why is this? The total costs are less and the dispatch numbers are better.