In those situations you can often see a player choosing a bigger club and basically forcing their own clubs hand to accept a lower bid than they would to a rival. Same reason you're more likely to sell players to a foreign league than to a PL rival for a premium, Coventry selling him to Boro weakens their team whilst strengthens Boro's, selling to us only weakens them.
Also with the player he mighn't be too fussed with going to Boro as they're just a mid table club at the minute comapred to us who are a full division better who he'd probably be desperate to move to. Like with Richy this summer with us, Spurs offered probably below what we'd have liked but he was desperate to move to a Champions League club, if Southampton or Wolves both came in and offered £60m we'd probably have rejected it, could've got more and he probably wouldn't have cared much to move.
Seeing the same thing with Gibbs White and Forest at the minute, £40m for him at the minute is a ridiculous price but Wolves have all the power, if even just Arsenal or someone wanted him though he'd probably go for £25m because he'd kick up a fuss. Same with Maddison to Newcastle for £50m+, another ridiculous sum.
These are actually prime examples of how unfair FFP and all that has been and why it's totally unbalanced against non established European clubs, the "top 6" can pay less for better players because of their allure of European football, an allure that they can guarantee because they can outspend other teams, teams that they can outspend becasue they can spend less for better. It's a vicious cycle.