The biggest cost driver for spare parts is the cost of storage space for parts which may not be required for a very long time. Also, if parts aren't held in stock, they would have to be manufactured specially in a probably very small production run requiring expensive extra tooling costs. Except for high turnover parts which can be sold somewhat cheaper because ancillary costs are not so high, we in the industry normally calculated a sales price approximately ten times what we paid for the same part as used for production purposes.