Ashley says he understands the Spaniard's unhappiness at not being able to land his preferred targets this summer, but adds that he is simply not able to compete financially with the biggest clubs in the top flight.
"If you said to me I am wealthy, in theory I am a billionaire or maybe a multi-billionaire - but in reality my wealth is all in Sports Direct shares," Ashley told Sky Sports News.
"As I said the other day, it is like wallpaper. I don't have that cash in the bank so I don't have the ability to write a cheque for £200m. I don't have it, it's simple.
"And I have to make it clear that I am nowhere near wealthy enough in football now to compete with the likes of Man City and others where it is a wealthy individual taking on what is the equivalent of countries. I cannot and I will not.
"Rafa knows that [the club does not have enough money] and it's not a secret. Every penny the club generates he can have, but it won't generate enough. Rafa makes all the final decisions on players out and players in but he has to do it with the money the club has."