Combined shipping for .99¢ shipping is dependent on how many cards are purchased (usually 4-5 standard base cards).
Value of combined cards must be less than $20 and has to be less than a quarter of an inch thick.
USPS Ground Advantage shipping is used once the order goes past the $20 value or cards are too thick to pass for .99$ shipping. This option starts around $5 and can combine unlimited amount of cards. This option cost varies by weight.
If you already paid for items separately, I'll refund you the difference if i combine shipping.