A 1 gram bar and a 1 kilo bar of the same purity don't carry the same premium per ounce. Here's how bar size actually affects your cost per unit of gold.
Short answer: larger bars generally carry a lower premium per ounce than smaller ones, since minting and packaging costs don't scale proportionally with weight — a 1 kilo bar typically costs less per ounce of gold than ten separate 100g bars of the same total weight, but larger bars sacrifice the flexibility to sell in smaller increments later, which is the real tradeoff to weigh, not just the headline premium.
Producing a 1 gram bar and a 1 kilo bar both require the same basic minting setup, assay certification, and packaging process — costs that are largely fixed regardless of weight. Spreading that fixed cost over a kilo of gold instead of a gram means a dramatically lower cost per unit of weight on the larger bar, which is the core reason bigger bars carry lower percentage premiums.
A single large bar can't be partially sold — you're committed to liquidating (or holding) the entire piece at once, which matters if you ever want to sell in smaller increments to meet a specific need rather than cashing in your entire holding. A collection of smaller bars, even at a somewhat higher aggregate premium, offers genuine flexibility a single large bar doesn't.
A large bar — particularly something like a 400 oz wholesale bar some refiners like Rand Refinery produce — represents a much larger single transaction, meaning authentication matters more and the pool of buyers able to purchase it outright is smaller than for a common 1 oz coin or bar.
The same "smaller units cost proportionally more" pattern applies to fractional coin sizes across virtually every series on this site — the economics of minting small units are simply less efficient than large ones, whether you're buying a bar or a coin.
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