For 99.9% of people, the funny of the prank would only hit later. Ie, upon finding out it was a prank, and hearing about the "insert 5 cents" part that they probably didn't see with their own eyes. Plus the retraction, and 2nd retraction. And reactions of other staff who fell for it (and caused chaos) before 8:30.
And then extra value upon retelling all of the above to others.
Someone relating that sequences of events to me as funny, especially if they said it was only funny after the pileup, would significantly adjust my prior as to dark triad characteristics in their psychology.
"prank" = IT guy sent campus wide email saying some printers will now charge $0.05/page
"that they probably didn't see with their own eyes" = they did not check physically very every printer on campus to verify none of the printers had the characteristic, the only way to falsify what the IT guy said, that some printers had a characteristic.
"Plus the retraction, and 2nd retraction." = 3x the time wasted for everyone on campus
"And reactions of other staff who fell for it" = people who believed the dry email from IT
"(and caused chaos)" = chaos isn't funny
"And then extra value upon retelling all of the above to others." = It sounds like we're assuming the relayer would get value from relating this, but the extra value is to the listener, it'd only harm the relayer.
As a listener, now I know that I have to verify 100% of everything the relayer tells me. They think a good prank is when you leverage your professional role to lie and cause chaos, which is justified because those poor sheep were complaining about something they didn't even verify with their own eyes. i.e. thousands of people should have gone through an absurdly onerous verification rather than trust communications you make in your professional role.
Me checking my inbox at 9:30am...
7:28 New Campus Policy printing now costs 5-cents per page
8:34 Re: New Campus Policy - April Fools! Printing is free.
9:14 Re: Re: New Campus Policy - Printing is still free, for now.
Absolutely.* Does that shed any light, here? They're not claiming it is a triviality, instead, quite specifically, they are claiming the funny part is chaos and the number of people who reacted differently.
* modulo marking the IT department as spam
The fact that you don't find the ensuing chaos amusing has me wondering - do you find Bedlam DL3 entertaining?
Note that finding something amusing isn't necessarily related to whether or not you feel the perpetrator conducted himself appropriately.