IMO, this type of scenario would be not just to think of the cost, but of the fish. The clown loaches, weather loach, and pictus catfish all have something to lose if housed with any non-ropefish bichir (their lives), while the bichir would also run a serious risk of dying because of the loaches and catfish having spikes that could kill it if eaten.
Even with my personal dislike for bichirs (that came about for the exact same issues this thread deals with! Perhaps that's noteworthy) notwithstanding, I don't think that's at all fair on the loaches and pictus catfish, plus the weather loach already provides an eel-like aspect and doesn't pose any risk to its tankmates nor is at any risk itself from dying after eating spiky prey.
Even with my personal dislike for bichirs (that came about for the exact same issues this thread deals with! Perhaps that's noteworthy) notwithstanding, I don't think that's at all fair on the loaches and pictus catfish, plus the weather loach already provides an eel-like aspect and doesn't pose any risk to its tankmates nor is at any risk itself from dying after eating spiky prey.