I think we'll be looking for at least 20 mill.
He's a full international, he's still young for a keeper and he's got a couple of years left on his contract. If we were selling a first choice player with those credentials then we'd be looking for astronomical amounts so for a second choice player I expect 20 million plus.
That would mean a new transfer record for Celtic.
If they do have 70 million in the bank (I'll trust you as you know more about the Scottish game than I do) then maybe they'll be prepared to splash that amount on him.
TBH. I had 20mill in my heed as well.
If the lad wants to go there, then Im sure they figure something out, loan to buy then payment plan or some such.
Could end up a bidding war though, as he will have a few options. But being an Irish lad, Im sure celtic would be a big pull for him.