Everton had an initial bid of £30m turned down but their improved offer - an initial £28m, rising to £34m with potential add-ons - was accepted.
Take the Iwobi deal there, Arsenal turned down 30m, why would they then accept 28m if they didnt think the add ons would bump it up to the amount they wanted? Im happy to admit that its unlikely that all add ons are achieved, as you say, no doubt theres a little bit of cream added on.
The only time ive seen the actual add-ons on deals have been the Rooney and Lukaku moves.
Would love to see the 1s involving our signings, personally I think they are appearance heavy.