I'll give Forever42 the post but this is really Gariig..
Those USB/Parallel cables are dirt cheap, I believe cost for BB is 3.00. They leave them out most of the time because it allows BB/CC/etc to make some money on your printer purchase. Let's say a HP 932c will cost 100-110 and sell for 130(I think it was something like that), this isn't much markup. However, this USB cable costs us 3 dollars and sells for 20, a HUGE markup. The cartridges are the same way, but not quite as bad, I think a 45A HP ink is like $10 and sells for $30. Some come with cables because the company is being nice for buying really expensive printers(MFPs) or the cabling is different then USB/IEEE such as the HP G series.
Gariig