Most existing models in supply chain management literature proving the potential of a vertical logistics collaboration decision see individual decision makers as fully rational agents. Nevertheless, literature review makes clear individuals are usually reluctant to change and in consequence they do not always respond to relative differences in a rational manner. The conducted Stated Preference experiment confirms this statement and shows that shippers leave beneficial collaboration opportunities unexploited because they have a certain level of resistance to intensify collaboration with their LSP. This inertia level is measured in terms of costs.