Moved into the existing fake pharms thread...
Fent can be expensive if you're seeking it out recreationally in small quantities for yourself, but it really can't be that hard for people to get or expensive for that matter because it is an extremely common cut used in east coast powder heroin. You're right it is very strong and extremely dangerous, that's why so many people die from it when a batch of dope that's made too strong goes around. It comes up in the news all the time and I have personally had some of that heroin myself. Because it is strong it is actually a cheap cut for these guys though because they don't have to add very much for people to feel it. And most dealers don't give a flying fuck if it's dangerous or not, they just want to make money they don't care about some junkies.
Now I don't personally know anything about the pills that you found so I can't say that is in fact what is in them, but it wouldn't surprise me to learn that. Do you think these ones are fake because they feel different when you take them or because you have never seen that marking before? Have you tried simply punching it into the pill identifier on drugs.com to see if it could be real? Sometimes some fakes look pretty real, but if the marking isn't even something that comes up when you search it then I'd assume that's a pretty good indication it's fake.