I had the credit card down to below $500 as of the beginning of June (I'm not even sure how I did that), then with the mid-June paycheck - poof! At 1.9% it was a very cheap loan. Here's how I did:
Original Amount -$3000.00
Rebate +$ 3.00
Interest Paid -$ 8.26
Bank Fee -$ 10.00
TOTAL COST $3015.26
The bank fee was caused by my own stupidity ... I waited to late to mail a check (I'm totally ETF all the way usually) and called in a check payment. They are the only one of my credit cards to CHARGE for that. Despite their awesome promo deal that experience soured me on this card (probably for good). I decided to pay it instead of risk losing my 1.9% rate on about half the balance. Lesson learned.
So borrowing this money could have only cost me $5.26, but even at $15.26 it's not too bad a deal since that money is up about $100 in my Roth account. Sweet.