Why are ETH transfers so expensive?

I've been noticing that transferring Ethereum, or ETH, has become increasingly costly in recent times. Could you elaborate on some of the key factors that contribute to the high cost of ETH transfers? Is it due to network congestion? Are the transaction fees being driven up by increased demand for ETH? Or is it simply a reflection of the overall market value of Ethereum? Understanding the underlying reasons behind the high transfer costs would greatly assist in making informed decisions in the crypto space.