We already paid part of the addons after reaching the Champions League semi final. I imagine his 40+ appearances last season paid some as well.Liverpool told the press they got thd full amount but they didn't.
Ten deals done in a similar manner defers payment of 50 milliion quid, some of which may never be paid if a player fails. By all accounts we have at least two now with Sterling & Sane. Maybe Stones is 3. That's just in one year. It's an enormous sum of money.
The brief was a £49m deal, which it is; £44m + a possible total of £5m. Without the addons the deal doesn't happen. So if Everton feel they can get the exact same deal, why accept £40m?