The article precisely says that "It is understood that Ferguson is on a short-term contract".. And the fact that she has prior top-end contracts with RM and TfL proves that she will not be there forever.

It's too easy to assume situations like this are 'at cost' to the taxpayer, it's probable that it is a net saving to the taxpayer.

It doesn´t make the decision wrong. It´s a supply and demand game isn´t it? It´s hard not to second guess in this matter, but you have to presume that the cost to replace them is much greater.

Exactly. A consultant's job is to deliver results from day one. If not, they're quickly out the door. The same can't be said for staff because they are considered an investment by their employer and therefore kept around much longer despite how much the drop off in "performance" may be compared to a consultant.