Prints per cartridge is based upon several factors that can be controlled by the operating system of the printer. For example, larger characters require more ink. As do formats which contain multiple lines of text, barcodes and graphics. Different font styles can also affect the cost per print.
As a rough guide, to print a batch code consisting of a single line of 3mm text containing 5 characters, you can expect to achieve 1 Million prints per cartridge. A best before date and batch number with a time code may be closer to 350-450K prints per cartridge.