It took 7 hours for the thugs to reach the daily ATM maximum limit? How do you buy expensive goods with an ATM card? That sounds completely bogus to me.
Mobile phones where not so common at the time ( circa 1995, Portugal), so the guy holding him couldn't tell how much money was in the bank account and how long his "partner" would take to empty it.
Large transactions are more difficult to pull than smaller ones and I guess the guy was sampling the limits of the card with reasonable sized chunks.
But to rationalize the actions of a heroin junkie is hard and I won't try.
