“When I was at university, the pay-for campus printers all worked on a system where you’d print your documents, release them at the printer, they’d print, then after they’ve finished printing, it would then contact the server to get the cost deducted from your balance.
That final step always took a while and I discovered in my first year that if I cancelled the print job as the final page was rolling out of the printer, it wouldn’t deduct the cost from my balance. With this method I got free printing for nearly two years before they upgraded the system!”
-PM_me_ur_navel_girl