Last time I asked around on 2.5G ethernet I was told to skip it and go to 10 Gigs straight as its "cheaper" and better than 2.5G. So I started to investigate and I am baffled by the costs. Let me break it down:

Quality 10G switch Mikrotik CRS305-1G-4S+IN ~150 $ (this seems reasonable)

10G SFP+ RJ45 modules - these are starting from 50$ on ebay from china which seems excessive, given i would need at least 4 of them.

10G NIC -Intel X540 T2 for around 40 $ if I want to go with RJ45. X520 with SFP+ connector can be had for 30$ but does not seem to worth it, given then price of SFP+ modules.

So I am somewhere around 430 $ for connecting my NAS and desktop PC via 10Gig. Compared to that, I can upgrade to 2.5G only for approx. 80 $

I could partially go with fiber instead of copper, pushing down the SFP+ module costs to 15$, but i still need at least one RJ45 module to run to my home PC. Also I am concerned fiber will bring some additional complexities that I am not prepared for (have zero experience with it).