Benny Hill's song about "cut out the middle-man" seems to apply here. If you want a large number of HP cartridges, then go to the maker. They tend to only part with such in container size lots, so that's "bulk."
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In closing, consider you may want to disclose what Country you are posting from.
Where is the best place to buy inkjet printer cartridges in bulk for a good price? I have an HP 3650. Thanks!