Think someones telling you sh!te. Any player is worth as much as the highest bidder is willing to pay. We will have a value on a player that will be the lowest price we're prepared to let him go for. In the case of Shinnie that figure will be based on value of player + value of youth development - any clauses built into an agreement with another team. If, on the other hand, a player requests a transfer, and such is granted then perhaps thats a kind of buy out figure.
Aberdeen, on the other hand, are on record today as saying they will not be splashing out on players. Having also recently signed defenders Ash Taylor and Shaleum Logan on free's they dont look like a team that'll pay out for anyone.