@hilde45 your perspective is similar to mine - assuming your interconnects and cables are half decent to begin with - the reality is that many are not. Steeply diminishing returns after say $500/m or so.
Now a brief rant about digital cables - these in particular are not worth spending more than a small investment ($300?). I’m a computing expert but not a networking expert but had a hunch that error correction in the protocols (plus the digital binary nature of the information) negates the traditional benefits of better copper and interconnects. One of my good buddies is a networking expert for one of the largest SPs in the USA. He cannot conceive of how say typical electrical signals could change the digital info enough for protocol correction to not work. if this were true, the Internet would not work - voice calls would not work, etc.