9.1.9 Calculating overall costs  Perhaps the most crucial point when making these decisions is calculation of costs. Unfortunately, no generally applicable concrete figures can be given in this context. In-house costs are difficult to assess as many institutions holding audiovisual collections have infrastructures available (rooms, air conditioning, intranet) the cost of which is incorporated into the general budget, which makes it difficult to calculate overall costs for transfer and/or permanent digital preservation. Labour costs differ significantly even in developed neighbouring countries, which weakens any general conclusions as regard price. Finally, services offered by professional vendors vary considerably, depending on the amount of items per carriers, their state of preservations and hence the possibility to automate the process. Cost of staff, equipment and other resources generally rise over time, while it is possible prices for some automated processes may reduce.  Because of the many factors related to a specific preservation project these guidelines refrain from any quotation of price ranges for transfer. These guidelines suggest that holders of collections acquaint themselves thoroughly with the specific situation in their countries or regions and observe the market situation on a constant basis.  When seeking prices for audio preservation services, tenders must be well prepared and defined in detail, and any subsequent offers carefully examined. Bids that offer the same service for a fraction of other vendors should be examined with extreme scepticism. Finally, outsourcing can only be successfully managed if a stringent quality assurance system, as described, is established, and any substandard work is rigorously rejected.