RFID is definitely going to be the more costly to implement, simply because it's newer. As of right now, there is not set "standard" for RFID, so the costs can vary wildly dependent upon vendor and the type of implementation.

Barcodes have been around since the day before forever, and (compared to RFID) is a relatively cheap system to implement. The only limitation is that someone has to physically scan-in (using your example), whereas an RFID tag (either in the person, on their clothing/badge) can scan-in as long as they are close enough to the reciever unit to send a decent signal.

According to Wikipedia (the source we all love to hate):
"It costs 0.5¢ (U.S.) to implement a barcode, while passive RFID still costs about 7¢ to 30¢ per tag."

I would assume that the upper range (30 cents per tag) refers to more complex implementations (i.e. keeping track of cattle on a farm).