I've got some Mellanox cards for about 20-30 USD each, some direct attach cable can be had for a few dollars as well. Later I picked up some cheap optical gear from FS[1] for when I moved my NAS into another room. About $20 for the transceivers and fiber cable was not expensive either.
Regular 1GbE is sooo low now.
Not got the switch yet, just running point to point. Using a different IP range so I'm sure I'm hitting that 10G goodness.
[1]: https://www.fs.com