There's an additional factor to consider as well: quality of construction.
Cheaper cables can tend to be inferior in areas such as strain relief, contact integrity, and general resistance to wear and tear.
A $5 cable with poor strain releif and tack soldering in the connector is no bargain if it shorts out after 6 months or 6 weeks because poor or no strain releif means the cable is easy to inadvetantly pull out the back of the connector, and there's no way to fix it because the cheap connector is sonically welded. Your choices at that point are to either replace the entire cable, or cut off the connector and replace it with a quality connector that costs more than the entire cable origially cost.
OTOH, a $20 cable that lasts you a virtual lifetime even when you accidentally run it over with your Hummer, and is easily reparable even if your Hummer does break it, will pay for itself in replacement and repair savings over the long haul.
That said, those cables you have appear to be heavily discounted at that $5 price. They are probably not awful cables; nothing to write home about, but nothing to lose sleep over either, I wouldn't think.
G.