A single colour cartridge works out expensive if you're printing mainly in black.
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Check how many pages the cartridge will print (cost per page).
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In many inkjets, the ink cartridge and print head are integrated into a single disposable unit. For high-volume inkjet printing, however, separate ink reservoirs are more economical.
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Don't pay extra for colour unless you really need it.
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Check which types of paper you can print on (different weights, envelopes, etc).
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The price if inkjet printers start at under £150, but running costs can be higher than other types of printers.