Engine costs are a big deal in F1, for the smaller teams in particular, as with substantial rules changes as we've seen in 2014 it is a cost that cannot easily be controlled. It is a high cost that you simply have to pay whereas other costs can be controlled far more easily. Staff salaries can be controlled, aero development can be controlled, component fabrication can be controlled. Sure, controlling some costs / working within a lower budget will almost certainly mean you fall behind others, but it is within your control. The engine isn't as controllable, and costs for 2014 certainly did increase. When your F1 team is a business with mostly fixed income, increasing the variable outgoings is very difficult to manage. Welcome to the world of Marussia and Caterham.