Beyond money, this is called a lack of professionalism. Perhaps not everyone knows that organizing even the worst show costs several thousand euros between stage rental and assembly (800 euros for an 8 x 6 stage), rental of all the equipment which is normally paid following the rule: rental = 20% of the cost - meaning a speaker that costs 1000 euros will be rented for 200, then the mixer, the outboard gear, cabling and looms, power boxes, lights, moving heads, not to mention the sound engineers etc. etc. Canceling a show at the last minute means wasting all the expenses incurred by the municipality (and thus by the citizens) and spitting in the face of all the professionals who set up the event by unloading and assembling thousands of kilograms of decidedly expensive equipment.
If I may express my opinion, anyone who behaves this way is merely a huge ignorant blowhard who thinks they are somebody special, but in reality, facts show that they are worth nothing. (But after all, we are talking about Teo Mammuccari, someone who became famous through prank calls, which most of us used to do at age 11! In short, he's certainly no Einstein)
But speaking of professionalism...
I remember my father when he told me about a Jazz concert in a park here in the Castelli Romani, I wasn't even born yet... The audience consisted solely of my father and my mother, but the artists played their entire program for them anyway. At the end of the concert, it is not difficult to imagine that my parents, being the only ones in attendance, approached the musicians (my dad is a drummer) saying they found it interesting that they had played despite there being practically no one in the audience. Their reply was this: "We play for passion and we were paid to do so; we would have played even if there had been no one, but we were pleased to do it for you".
That is class, honor, and professionalism! I believe that certain individuals who think they are "Christ on earth" should come down from their clouds and take an example from these people who earn figures with a few fewer zeros than them. To make a long story short, Mammuccari like others debut with these "theatrical acts" to put on airs, believing that their image would be compromised if they found themselves performing their duties for too small an audience. The problem is that they are so stupid that they don't realize that this is, on the contrary, exactly the right way to damage their "supposed" image!!