For small office/home setups, 10-gigabit networking is probably a lot cheaper than you think. For larger environments, it’s certainly going to cost more, but also your IT costs should be a smaller percent relative to human/salary budgets. (If you’re in a “real” office without 10gbit, and you throw a lot of data around to network resources–get it fixed).
Gigabit isn’t that fast! You’ll see ~100MB/s on network transfers. Ever needed to temporarily move a few terabytes from a computer so you could reformat it? It’s painful. Back in the days when most HDs could read/write at a little north of 100MB/s, it wasn’t as noticeable. These days, SSDs, multiple-HD arrays, and especially NVMe drives blow way past that limit.
The cheapest possible 10gbe setup is to directly link two hosts. Very commonly, this is a single server and some network attached storage device. For that, you will need: