Spinning HDDs are faster than this as well, 250-300 MB/s sequential read seems common per drive, and in a home setup you might have a couple of those in a RAID-1 giving 500-600 MB/s read BW.
Right, for 2x single stream sequential read throughput + redundancy I guess you need somehing like Linux f2 RAID10 mode. Otherwise reading every other stripe per disk would kill you due to seeks or 50% wasted readahead.
Well, seeing how large SSDs are still very expensive (in my mind it's €100 / TB), my hunch would be that if it makes sense for you to spend that much money on the drives, you probably won't really notice the price of a couple of 10 Gb network cards. They seem quite cheap on eBay if you're OK with used.
The Mikrotiks are pretty reasonably priced (though you need adapters to go to RJ45, and you can only populate every other port due to heat). But you're right, the low end of switches are generally 10-20x more expensive IME.
NAS with HDD and a boat load of RAM can easily saturate 10GbE NIC if you're using it as a media server. Most content on my NAS is cached and rarely touches the disk.
Also, the main competition is WiFi which is significantly slower than 1GbE in most cases.