That’s not really low priced, when you start to include the extras, a bit more power etc.
You can get better priced used PC’s where a quad port card can be added, that’s what I mainly see missing in these type of solutions, I want 4 to 6 NIC ports.
If the Ethernet LAN is not from Intel, it won’t play well with pfSense/Opnsense or any other BSD firewall.
If your looking for low, low prices with a intel 4 port nic (Pro/1000 PT/ET or i340) for 169.00 + 30.95 shipping. Or he has cheaper ones with 2 port intel cards. Or get a one of the protecti type models from alibaba.
(HP// T620 PLUS Thin Client Quad Core GX-420CA 4/16+Intel 4PORT GB -pfSense ready | eBay)
protectli is pretty good
Hmmm… quite a few choices out there near the same price … I stand corrected 
I have one from the seller Cudzu linked, has been working fine for light weight functions at my home for over a year.
I am told that you can find slightly more powerful HP T730 versions for similar prices, but I have not chased this down yet.
Last month i bought this nice little system from amazon, with quad core cpu and dual channel memory, after i saw this review:
This is exactly what I did. I bought a protectly barebones and just got a cheap m.2 sata with 2GB of ram. Works flawless. About 200 bucks, pushes gigabits.
I got this as well. It works quite well on my 1 Gbps cable connection.
Gets hot running pfsense? How much load are you putting on it?
Nothing… just idling around 2-4%… when I had the issues with pfblocker where it would go up till 25% and stay there… cpu temps went to 70C… This box is fanless… The outher box (metal) gets hot… around 40-50C I would say touching it.
Currently I have a fan blowing over it. It’s 35C overhere anyways so its on anyway. That cools down the case to around 40C (CPU) which is acceptable. I’ll probably get some cheap 8 euro fan from ali express to blow the air off the top which should do the trick.
I also need to check the thermal paste which is probably very bad