In Kenya, the largest note issued by their central bank is the 1,000 shilling (KES) note.  That's worth about $12.  Cash is still used widely for making purchases such as appliances, used cars, etc.  Imagine going shopping for a new large screen TV and having to carry a 3" thick stack of bills.

Then imagine being the merchant, having to carry a satchel to transport the previous day's cash sales to the bank.

This idea has potential.