Much of the transfer value is determined by how much the player has left in their contract, what they are getting paid, and the cost of development, i.e. Compensation. The value can be driven up if the player is in demand, so clubs have to bid against each other. Selling guys with a year left on their deal to the only club that wants them isn't going to generate millions.
Other clubs aren't out there to do us a favour, if they are low-balling us we can always reject it, but there's more to it than that. Also, clubs dont just rely the well society q&a on periscope or quotes in the sun to know our situation, clubs do their homework.