And the boss has also told clubs keen on Matheus Pereira and Sam Johnstone that the Baggies will not sell any of their stars on the cheap.
Despite Albion having been relegated from the Premier League, Yokuslu and Diagne have made a big impact since arriving on loan from Celta Vigo and Galatasaray respectively.
But while fans would like them to stay and lead a promotion push, Allardyce believes the club cannot afford them.
“The reason Okay and Mbaye came here is to show they can play in the Premier League,” the boss said.
“Why else would you come? Why would you leave Galatasaray as leading goalscorer, or a side that isn’t struggling against relegation in Spain.
“Why would you come to the Premier League, other than to make an impression, to say here I am, look at me. Come and get me.
“That would hopefully have been us had we stayed up. (But now) we couldn’t afford them. We have to go to Championship wages now so those players are very difficult to afford.”
Both Pereira and Johnstone have shone this season despite Albion’s struggles.
A host of clubs are believed to want to keep them in the Premier League – but Allardyce insists they will not be sold on the cheap.
“There will always be somebody watching now we’re relegated,” the boss said.
“There’ll always be someone saying ‘what cherry can we pick at West Brom?’
“There are some cherries to pick but you won’t pick them cheap.
“There are a lot of them worth a lot of money.
“I have one of the best goalies in the Premier League for sure, without any question of a doubt.
“I’ve worked with Pickford at Everton, who’s now the England No1, and he’s right up there.
“And with all the other goalkeepers I’ve seen, and you can mention all the foreign goalkeepers too, he’s right up with them.
But because he’s Sam Johnstone in a struggling club at West Brom, he hasn’t got the accreditation – apart from the fact that Gareth (Southgate) has seen him at England and seen what he can do and knows he’s good enough to go in that England squad.
“He’d certainly be good enough to go to the Euros.
“There are other players too. The emergence of Matheus Pereira is no shock to me.
“He has continued to try his very best to keep this club up.
“That goal against Arsenal, what does that tell you about him?
“It tells you without any question that he has the right quality to play in the Premier League. No question about that.
“But no cherry-picking, The club would only let them go if they get what they’re valued at."