That used laptop might be worth a year of disposable income in some parts of the world. And temptations are had to resist when others understand that you can replace it after a single week of working.
> You can use plastic to avoid ever having large sums of cash on you.
No, in most parts of the world you cannot rely on plastic. Heck, even in Uruguay ("the Switzerland of South America") I had to take a bus for 1 hour to get to the next ATM; nobody in my beach side town would accept credit cards. The trick in such parts of the world is to distribute your money evenly into various pockets and bags and to have one dedicated pocket where you keep what you need for the day in small denominations so you don't have to flash an average, monthly, local salary when trying to pay for a roadside snack.