On purchases of the following with the Blue Nile Credit Card. 6 months. $500.00 - $1,499.99. 12 months. $1,500.00 and up. 18 months. (for Astor by Blue Nile™) $2,000.00 and up. Option 2: 9.99% APR for 24, 36, 48, or 60 months..