I've been working as a controls engineer at integration shops for close to a decade, and had the exact OPPOSITE reaction. The price is ridiculously cheap!
Your serial to IP adapters are one use case where this could be used, and are one of the few things I've installed that was cheaper than this. If the machine needs a true PC for config/calibration software, displaying vision results from industrial camera, or reading/writing data to a plant network, the typical answer is an OnLogic ML100G-51 industrial fanless PC at $850. Sometimes the answer will be a PLC in with a built-in PC, like a Siemens S7-1500 or Beckhoff CX2020 at close to $3,000. Often, you also need an operator interface, which is usually some variant of a Windows CE computer bolted to a rugged touchscreen, and run between $500 for an off-brand 7" display to a $1500 software license plus that OnLogic PC plus a $500 or more large-format touchscreen. However, if the PLC needs to communicate with a USB or serial device like a barcode scanner, I'd reach for a Real Time Automation 435USB module at $640, which is basically the same as one of these. To remote into the machine we recommend every customer get a $600 Ewon Cosy industrial VPN appliance, it's an easy sell at less than the price of most service calls. If it needs a small camera, a $2000 smart camera marries a little ARM processor to a low-resolution monochrome sensor, or you connect GigE cameras to a higher-power vision processor for double that.
If you're going to sell 10,000 units to fill a particular industrial niche, you can injection mold your own DIN rail enclosure, make your own baseboard for 24V screw terminal connections and which might use a Pi Compute module or fully integrate a little ARM processor, and which will hide any of the details from end customers behind "no user serviceable parts inside" and "warranty void" stickers.
All of the above do essentially what a $35 RaspberryPi and a bit of Python scripting could do, but with a warranty, enclosure, manufacturer support, vendor support, and user manuals that customer maintenance departments can use. All of those are valued by many careful customers, but for half the price this is interesting enough to pay an engineer for a couple hours of custom work. For sales purposes, these go into the panel with 24V screw terminals and DIN rail mounting that checks off industrial standards conformance and don't look as crappy as wall warts and custom brackets. Those are the devices this thing is competing with.