Everton were reportedly on the brink of signing Delph last month, while Fulham and Sunderland have also shown an interest.
However, while Grayson accepts Premier League clubs will be keen to sign the 18-year-old, he insists he will not be leaving on the cheap.
"Until someone comes in with hard cash and there's an offer on the table, then that's a decision we will eventually have to make," Grayson told Sky Sports News.
"There have been lots of enquiries, but we want to keep hold of the player.
"Then again, every player has got a price. Man Utd got a good price for Cristiano Ronaldo and no-one expected him to leave six months ago, but in football that happens.
"He's a talented player and you can't get away from the fact there are going to be some Premier League clubs enquiring about him, but he's under contract and any decision on players leaving the football club has got to be the right decision for us and the player as well.
"Everybody is still here, but in football you never say never, and you're not sure what's around the corner with any players."
Grayson is also waiting for offers for Beckford after the striker was placed on the transfer list after rejecting an extension to his contract which expires next summer.
He added: "We put him on the transfer list in the summer because he turned down a new contract.
"We've had a few enquiries, but nothing concrete on the table. It is a difficult situation going into the last year of his contract.
"If we do get an offer, do we sell him or do we keep him and he scores the goals like he has done over the last two years?"