The Pen is mightier than the Sword

Got a mailer recently from UOB Cashplus.

Essentially the deal is one will get a free mont blanc pen worth $300 if one maintains a minimum debit balance of $1,000 with UOB at the promotion interest rate of 1% per month.

I was thinking, this doesn't sounds right, and i'm tempted to take UOB up on their offer.

Imagine, if i withdraw $1,000, i incur interest charge of $10 [1% * $1,000]. In return i get a free mont blanc pen. [i wouldn't put much faith in the $300, but i'm sure it's worth more than $10]

What's the catch? i read all the fine prints, don't think i can see anything. All i have to do, is remember to credit back all the money i've withdrawn, and voila. Good business for me.

I suppose the bank wishes for people to start using their revolving facilities, so that they can earn more interest from common folks like me.