It'll just be Celtic posturing for a couple of reasons. He's their prized asset and while they're wealthy in Scottish terms they're not wealthy compared to the top leagues in Europe so £25m would be very hard to turn down but he's the only player they have worth top money so they'll want to maximise it. They don't have huge money to pay on transfers, they only signed Odsonne Edouard from PSG as they had the kick back from VVD going to Liverpool, an extra £25m could buy them some very good players at that level. They'll also want to appease the fans, he's a fans favourite so they need to convince them that the money was too good to turn down, letting him go for £22m without a fight isn't going to do that.
I wouldn't be surprised if they came back to us, one way or another I think it'll still happen. We're not walking away for the sake of £3-4m even if it means the deal is broken down in a different way.