By Euan Burns It is fair to say that Manchester United have not been famed for their smart decisions in the transfer market over the past decade or so. The club have made several incredibly expensive mistakes, and it has created a feeling among some of the fanbase that it isn’t worth getting excited about a new player until they have impressed for at least six months straight. Man Utd’s ten most expensive signings have cumulatively cost the club just under £700m in transfer fees before you get on to wages, agents fees and everything else. With that in mind, let’s see if we can decide which dea…