Calafiori is not 100% to Arsenal yet.
Bologna wants 50mil €, according to rumors Arsenal offered 40€.
The deal is not done yet but if they really wants the player I can't see a big problem for them reaching 45m€, they are in premier they have a lot of money after all.
During lockdown period, like 2020 and a bit after, a lot of teams spent a lot of money on players, we have seen 100+ a few times, and a lot of money spent. The jokes about "oh we were gonna ask 40, but they offered 60" happened a lot, mainly with United but many teams as well. We are seeing now even bigger clubs are trying to make sure they are financially stable, and not go with Barcelona route or United issues.
Arsenal can certainly afford to pay up 50, that's nothing to them, well not nothing but if they want a player enough to pay up 40, they can afford to pay 50 as well, that little 10 million difference is nothing to them for real. However, they still haggle because premier league clubs got a lot richer lately and that causes a lot of trouble. The TV rights yearly is nearly 2 billion dollars, so everyone is getting a ton of money, at some point I remember premier league winner got more money than UCL winner.
So all in all, they realize they can't just be pegged for more money all the time, and decided that they would rather go back on an offer and find other players until they find one of value, instead of keep going around overpaying for players at all times for no reason at all.