Look at the used markets as well, especially the 8 port variant can sometimes be found for 15-20 EUR/ USD.
Keep in mind that these are predominantly switches, while you can use them for routing, they're not very fast at that; maximum firmware size (dual-firmware) is 6976 KB for kernel+rootfs+overlay, not plenty but useful. The switch is easy to open (3 standard phillips head screws, slide off the top, populated/ marked 3.3V serial header (2.54 mm spacing)) and pretty robust/ hard to brick.
As all devices of the realtek target, initial access to the management interface is slightly tricky, as LAN is only available via VID 100 on port 1 (see Support for RTL838x based managed switches - #367 by slh for details, https://github.com/openwrt/openwrt/pull/3860 and https://biot.com/switches/gs1900-8 may also provide further information).