@andreaboi.eth
What model do you have? Well depends... my in-ear monitors cable is more expensive and it's worth it but is not a fancy audiophile one, is the standard cable which come to most premium and high-end custom iems with T2 connector. For my Focal I use Tripowin GranVia XLR, for Sennheiser should be around $50 for classic 3.5mm jack, a very well made cable for the price.