Have you paid any attention at all to Moshiri's tenure? This is a club that got a points deduction because they hadn't read the rules about what they were and weren't allowed to do. Ancelotti and Brands both suggested they'd been lied to about what we were doing, Dyche said he could write a book on the madness that's gone on behind the scenes, players like El Ghazi have been signed clearly over the head of manager and DoF. The DoF not being entirely sure what he's got to work with would be small fry compared to some of the stuff going on over the last few years.Sorry but I refuse to believe that when bidding for a player the DoF doesn't actually know how much money they have to bid with.
Basically there are 2 options to cover what you're saying. The DoF knows he only has £10m to spend but spends all summer bidding £30m despite knowing he doesn't have it (for the bantz maybe?) or the DoF believes that £30m deals are doable but actually when push comes to shove it turns out they aren't. Quite how you've concluded that option A is infinitely more likely than option B I don't really know to be honest.