My reading of the situation is that we want to top-load with add-ons and bonus payments up to about £23m and Celtic are wanting £25m up front. It's not that we're squirming over £2m. We just want some financial protection in the deal and Celtic want top dollar up front for their star player. Fair play to both sides.
On top of that, and referencing what @Thomas
have been talking about:
Tierney may not want to leave Celtic and will not kick up a fuss if his board don't sanction it - exactly like Baines & United when Moyes went there.
But that's not the same as prefering to stay. He'll be ambivilent about it. He'll want to come to the premier league. He'll want the wages we have offered (although, let's be fair, we've probably already agreed the wages with him via his agent). but if it doesn't happen? He gets to spend another year with his boyhood club. He's ok with either situation.