The price of Lophiosilurus has increased very significantly in a few years for a reason I'm not well aware of. As far as the breeding is concerned, I believe they are an esteemed food fish in their native region and I believe that this could be to cater to that demand. Yeah Fowleri are pretty scarce on the market nowadays I'd agree.
I did consider getting a Rhinodoras but was uncertain as to whether I'd get an adult with spots as opposed to bands if I were to grow out one a juvenile. I prefer the spotted variant. Would you consider both your Rhinodoras and Franciscodoras to be relatively model citizens with little aggression? This was also a concern of mine as I've seen a video of two Franciscodoras displaying what seems to be territorial aggression against each other.
As for my Wertheimeria, I'm presuming its female as its getting somewhat chonky. I'd say that it has roughly grown double the length when I first got it a year or so ago, and it is currently around 6 inches in length. In terms of growth rate, it's been non linear. Currently it's having a growth spurt both lengthwise and width wise and it has gained quite an appetite. I feed it massivore pellets and I believe it also does eat very small mollies and ghost shrimp opportunistically. As for shyness around food, I don't note that, but it could be due to generally peaceful, non competitive tank mates. It enjoys small spaces, constantly pressing itself against the glass on one end and an aquarium pot on another. I would say that it has been a rather peaceful fish thus far, and has also learnt to be accustomed to touch as well. All in all, one of my favourite fish!