The manufacturer of these PSUs is in Thailand or Korea, IIRC. I contacted them some years ago, as they seemed to be the only ones making a suitable PSU with 48V besides the 5V and +/-15V. They seem to have an agreement with RME not to sell those, except to RME. But the price was just a bit lower than RME sells them, so I just ordered the one I needed from RME.
Mind you, this was in FF800 days, so things could've changed since then. The FF400 doesn't have a built-in 230VAC PSU, works on Firewire bus power or external 12 to 16 V. It still has an internal PSU that generates the necessary voltages that has the same problem with electrolytics after years in a hot rack. MOTU seems to have the same problem, so it's certainly not exclusive to RME.