Three points:
1) Tonight I'll have my third pastrami sandwich for dinner. That's how much meat was included in my $27 sandwich. There's a long counter with eight carvers. You chose a carver and get on his line. When it's your turn you tell him what you'd like. It's useful to be putting a couple of bucks in the tip jar as you order and engage in clever banter. I told the carver that I needed a plastic bag as I was taking the subway home and didn't want to be attacked. Note that the pastrami is carved and not put in a slicer.
2) As noted....you get a ticket and the carver wrote the sandwich price on the back. They only take cash and I saw several people directed to the ATM machine in the back. If you never leave Katz's then you never have to pay.
3) Most of the classic NYC delis have closed. (Carnegie, Stage, Wolfe's, etc) However each time I've gone to Katz's it's been packed...sometimes with a line outside.
Maybe they'll eventually have "Beyond Pastrami" for Walt.