There are couple of things that need to be prepared in advanced and take time have been purchased but overall majority which can be done days before have not been purchased.
You don't understand qusp: the more people there is the less each person have to pay for the venue. Just logic as the venue is fixed cost. So say a room was $100 then 10 people would have to pay $10 each but with 100 people per person price is $1. Also cups and napkin all sell in bulk and more people there are the cheaper it becomes until I reach threshold where i have to buy another bulk.
Regarding baby wipes, I know how expensive it is but if I buy in bulk, then it is cheaper. And with all the expensive gears at the meet, I see this as essential, that I could provide. And you maybe fine with tissue stuck on your pizza, but I believe there will people who prefer napkin over tissue any day and are not fine with tissue.