Here's what I've seen when I've used Foma films:
They're all slower than box speed, because they were not designed for normal contrast at box speed in MQ developers, as it's stated by their manufacturer.
From this point of view, Foma films are not the best films in the world, to say it politely.
In my case, the only Foma film that's more or less usable is Foma100, because even if it's slow, when we use tripod with MF or LF, real speed (losing a stop) is not as relevant as when we do fast handheld photography with ISO400 films.
If I'm doing that -detailed tripod images- I have no reason to use Foma200: Foma100 is better.
The worst one in my opinion is Foma400: not even close to Kodak's and Ilford's ISO400 films... It's slow, grainy, and reaching 400 is a push already, so when we try to get EI800 or EI1600, it becomes the worst ISO400 black and white film I've used... If I want grain I prefer Tri-X, and in that case even Kentmere400 and Ilford Pan400 are much better films than Foma400.
Are Foma films cheap? Not at all: after we pay for them, we have inferior tools in our hands, compared to other films.
And then quality/manufacturing control is world known low. And apart from that, Foma films have native scratches and other emulsion defects often, not to mention they get scratched easily too.
ISO400 films are called fast films for a reason: their ability to offer good results after pushing 1-2 stops in MQ/Speed enhancing developers: Foma400 doesn't belong to that group: it's just for EI200 photography: I don't do that: if I focus and/or use tripod, I prefer best ISO100 films at EI50, and if I do fast photography, I prefer best ISO400 films at EI640.
In my opinion Foma400 is aimed at people who don't print in the darkroom but scan, so they don't need best tone in negative because they adjust that after digitally photographing the film with a scanner, defining new digital tone from then on, and it's aimed mostly at students, third world, and other people who prefer lowest prices as their priority,
Again in my opinion: best ISO400 films are TMY, TX, HP5+ and Delta400, all of them sharing the first place. In a second place, IlfordPan400. Third place: Kentmere400. Foma400 is in the fourth place, but it can't do what the other six do.
My recommendation: if you'll use tripod or wide aperture focusing, you can use Foma100 at EI50, though TMX, Delta100 and FP4+ are nicer films, and if you want to work at EI200, you can buy Foma400, though all ISO400 films are better. And if you want to do fast photography, forget Foma400 and get Ilford and Kodak ISO400 films.