We are a long, long way from requiring a mark to buy or sell. Best of all, certain classes of people will always do business cash-only, no questions asked, regardless of what is being sold. One of the coolest scenes in Alien Resurrection isn't about space monsters. It's a simple business transaction. A corrupt general paying a pirate for very illegal wares.
"These were very hard to come by."
"So was our cargo."

"Just saying very few people deal in cash nowadays"
" Just the ones don't like to keep business records."