I know that many printers that come supplied with cartridges have 'special cartridges' that are about half full. I believe that this is so that the machine is up and running before you have to fork out on new ones.
However, when I purchased my Magic2 - also from Argos - about 12 months ago, the inkfilm lasted me about a week. I work from home and receive many faxes, but replacements tend to last about 3 weeks. I no longer buy the original replacements and use Viking Direct:
Next day delivery [free for orders over £30], good service and excellent, no quibble returns policy. Cost is just £10.99+VAT for a box of 2 rolls
Hope that this helps.