Invoice amount calculation method, invoice amount calculation device, and printer invoicing system

An invoice amount calculation device for an inkjet printer that performs maintenance accompanied by ink consumption, the device comprising:

• an actual print volume acquisition unit that acquires an actual print volume PV, which is the amount of ink used for actual printing not including maintenance during a specific period L1;
• an actual print volume evaluation unit that determines if the actual print volume PV is less than or equal to a specific volume V1;
• and
• an invoice amount calculation unit that calculates an invoice amount according to the actual print volume PV, the invoice amount calculation unit
• calculating a first invoice amount, which is a fixed amount, as the invoice amount when the actual print volume PV is less than or equal to the specific volume V1, and
• calculating a second invoice amount based on the actual print volume PV as the invoice amount when the actual print volume PV exceeds the specific volume V1.