[JJMcJ]

Bob has a business with lots of cash coming in and can fold Beth's cash in without it being too obvious.

Or Bob knows people who know what to do with suitcases full of $500 Euro notes without alerting legal issues.

Presumably Beth pays Bob for this service.

Then Bob may have to pay his friends.

This can be done with varying degrees of sophistication.

[azinman2]

You just described money laundering. But where does Turo fit in?

[JJMcJ]

Often it's more for tax evasion. Beth pays for cars as a business expense.

Bob just happens to have the Cayman Islands as the business location.

Money flows from U.S. business as a deductible expense, to the location out of the IRS's reach.

Or there isn't one Beth but lots of people with dodgy credit cards from banks in weird places. Those card holders indeed get their money in suitcases full of folding money, pay for their "rentals" and so the money flows into legitimate commerce. Bob of course pays for this.