Guitar Center offers a selection of instrument and microphone cables for $5, as listed below. Opt for in-store pickup to dodge the $4.98 shipping fee. That puts each at $21 off list and the lowest total price we could find. The deals:
Musician's Gear XLR 20-Foot Microphone Cable (pictured) for $5 (search via "100341862")
Musician's Gear 18.5-Foot Instrument Cable for $5 (search via "100044584")
Musician's Gear 18.5-Foot Woven Instrument Cable for $5 (search via "105766836")
Frugal isn't smart if you put off replacing these things. Waiting too long can cost money or even endanger your health.