Very similar-looking belts sometimes vary widely in cost. The quality of the leather is one common factor: calfskin is the most common material used for belts, and a good belt will have a soft, supple leather. Flex the belt to make sure it hasn't turned brittle or started to crack. Another good test of leather is to score the back very lightly with your fingernail — if a faint line appears, the leather is still soft and fresh. Old, hard leather will resist your nail.
Construction is the other major factor affecting the price of a belt. Look for small, tight stitching with no loose ends wherever the leather has been sewn. Buckles attached with a snap on the back of the belt can be changed out, while a buckle stitched in place is the only one you can wear with the belt — some men may find the flexibility of a snapped belt worth paying more for, especially in good leather. Belts can be custom-cut at some leather goods stores.
Brand name will also play a factor, but means quite a bit less than the other factors. Your belt is too small for most people to be able to tell at a glance whether it's designer or not. Spend the money on quality instead.