The basic assumption of much economic analysis is general and costbenefit analysis in particular that prices bear some specific relationship to real, or opportunity, costs has already been shown to be a dangerous one to make in transport appraisal. In any particular appraisal, the analyst must regard sceptically all the financial data with which he is presented. As the examples below will show, this process is an important if not central one in the transport sector. This is an important point when the contribution of economic analysis to decision-making is being appraised. First, of course, it means that economic analysis can have a useful contribution, even where there are items of benefit/generalised cost which are not readily measured in money terms or where no such items are involved: and second, that any form of analysis which rely on uncritical use of financial data must to some extent be suspect. Financial information is rarely as hard as it seems to be.