Why is a 6.5x6.5 inch postcard more expensive than a 6x6 inch postcard?

The price gap comes down to how efficiently each size fits on the large press sheet the job is printed on. Even a small size change can cross a threshold that leaves more of the sheet unused.

• 6 x 6 in: nests more pieces per sheet, so there is little waste and a lower cost per card
• 6.5 x 6.5 in: fits only two per sheet in this case, so a lot of paper is trimmed away and the cost per card rises

If budget matters, a standard size that packs tightly on the sheet almost always prints cheaper than a slightly larger custom size. Ask your printer which nearby size fits the sheet better.