I can share some experience about the mentioned problem
As I must deal with EP4CE115F29I7N, the only source appears to be Aliexpress. But not, a bit later about
This one BGA highly differs in appearance on Aliexpress. Some of them look fake, but they work like a charm and vice versa
Last year the price on this BGA was around 30USD, plus minus. Then in summer it starts to rise, when this spring reaches actual crazy prices. But there is another problem. I don't know where Aliexpress got their chips, but there are a lot of defective
My personal experience is two in row from a "reputable" seller with 100% feedback. And I know two more such cases. For actual prices it is highly painful
Lucky for me, I jump in the last cheap train
OK, I need those chips, what to do
OK, let's try Alibaba
Bingo, there are a lot of cheaper offers. Even for 50EUR for a piece, but... refurbished. Very high risk. So finally I found nice looking chips for 185EUR with delivery and taxes
Just I hadn't time to check it. I.e. solder the board and test it, just BGA are in place
Prices on other parts are just crazy as well
If just price, but counterfeit chips as well
Three LMZ22005TZX burn out in row. Check actual prices... When I order a replacement from another seller, that chips highly differs. Replacement works much better