What's stopping us from adding a repeater every couple of feet? Transistors aren't expensive and integrating it into the cable shouldn't be too difficult.
You could also do 25gb x 4 and aggregate at probably 1/3 price. You could upgrade later, without changing fiber. You could also go with the switch but use 25g transceivers, and upgrade the transceivers later. This is about 60% cost.
In a year this will all be half that price. USB4 plus a ton of repeaters plus … is going to dwarf the initial cost of 100g fiber quickly. In 5 years, you will probably be able to run 800g over the same fiber if you are bored. A or aggregate 100g links. You would have to replace all the USB with new USB-9 2x2.4 SE stuff.
If you think it's cheap make one and get rich.
But it's most certainly not cheap or easy or low cost.
The cheapest way to do this is over OS2 fiber. Look up how much money you have to spend to get 2x 100gbps OS2 PHYs and 2x 100gbps QSFP28 cards.
That's a strange argument, given that USB devices and your USB ports and CPU need a multiple of the amount of transistors in a repeater to process these signals.