Hibs would rightly laugh in the face of a 500k bid. That's maybe 2 places in the league, reaching a cup semi final, or reaching an extra round in Europe. These are all things Mcginn would make more likely to happen. We'd literally be better off letting him leave for nothing next season. I'd also suspect that Celtic would end up having to spend more to get him if he was out of contract than 500k since he'd have lots of other bids driving up his wage demands.