I can't see any sense in Terry wanting to go to pastures new. Sure he might be offered more money at the likes of Barnsley but would he end up with more and is that really what he wants in any case? If he wants to stay, I am pretty sure his future is secure here for some time to come, during which time he will be on a good wage. He may be able to earn more elsewhere but that could be pretty short term and unless he produced positive improvements, he could soon find himself out of a job again and unable to command the same sort of salary in another post. In any case, at his age and with his background and other interests he should be financially very secure by now.
My feeling is that the money isn't actually that important to him as long as he has enough to live comfortably (which he has). He likes to be in the limelight and I am sure he would love to win a national trophy and manage a team in Europe. He won't get that at Barnsley, or Wolves or any other Championship side but he may well get that at Inverness. And being associated with a team that is challenging for those honours (albeit in a far less competitive league than in England) he maintains a higher profile for his wider interests.
If he achieves success here, then he will be in the shop window for a seriously bigger club and I wouldn't blame him then for moving on and trying his hand at the top level before he retires. But to move to a championship side at his time of life just makes no sense. If he wants to win something then he needs to stay here.