If you think about it, it's quite impossible for Barcelona to buy him if he doesn't show good performance. His sales are still quite high for Barcelona and he also has a high salary, while Barcelona doesn't have stable finances. So I think Barcelona management is only borrowing him for this season as a substitute option and Barcelona has no real intention of buying him.
You have a point, Barcelona's finances is really making them miss out on a lot of talents that's why they always end up loaning players and always depending on their academy players. If Rashford doesn't show good performance he is definitely going back to Manchester United and even if he performs well I don't think they will have the money to retain him but until then let's just see how he will perform.
Rashford was not their main target, it was Nico Williams and I wonder why Williams didn't show much interest and later signed a 10 year contract with Bilbao. From my observations I think Nico Williams is not confident in himself. He feels he might not perform the way they are expecting him to if he moves to Barcelona. That might be the exact reason why Barcelona never pushed more to sign him, despite being the first choice for the left wing. As for Rashford, I have a strong feeling he will do well at Barca.
Maybe Nico was offered a much higher salary which Barcelona can't afford to pay him currently or could be anything, no one knows his reasons. If not for form Rashford is a much better option than Nico, he scores a lot of goals and also a very skillful player. I also have same feeling that Rashford will do well at Barcelona because he plays a much similar style to them and will enjoy all the spaces they create.
I actually thought of this, and I told someone maybe this is one of the reasons why the Nico Williams deal was not possible.
maybe Nico Williams feels he won’t meet up with the expectations.
Nico will be able to perform well so I don't think that's why he didn't join. He's already friends with most the players so he will easily adapt to their game. Maybe Barcelona knew they can't afford him that's why they never pushed hard.