A one ounce bar and a kilo bar contain the same metal, but the small bar costs noticeably more for every ounce inside it. The gap comes from fabrication economics rather than from any difference in the metal itself.
Fabrication costs do not scale with size
Producing a bar involves a fixed sequence of operations: melting, casting or stamping, weighing, assaying, serialising and packaging. Most of that work takes similar effort whatever the finished weight turns out to be.
A refinery spreads those fixed steps across the ounces in the finished product. A kilo bar carries them across roughly thirty two ounces, while a one ounce bar carries the whole burden alone.
The result is a fabrication charge per ounce that rises steeply as bar size falls, and that charge is passed down the chain to whoever buys the finished piece.
Packaging and handling add another layer
Small bars are usually sealed in tamper evident cards carrying an assay statement. That packaging is itself manufactured, printed and matched to a serial number before it leaves the refinery.
Every unit then has to be counted, inspected and stored individually. A dealer moving a hundred one ounce bars performs a hundred times the handling of a single kilo bar.
Those costs sit inside the dealer premium rather than in the quoted metal price, which is why a spot figure alone never explains what a buyer actually pays at the counter.
Demand for small units is steadier than for large ones
Small bars and coins are what individual buyers can afford, so demand for them is broad and persistent rather than episodic.
Large bars are bought mainly by institutions and vault operators, whose purchases arrive in blocks and pause for long stretches. Steady demand supports a firmer premium than lumpy demand does.
During periods of heavy retail buying, refineries reach capacity on small formats first, and premiums on those sizes widen well before large bar premiums move at all.
Part of the premium comes back on sale
A dealer buying small bars back will usually bid above spot for them, because the dealer can resell them into the same steady retail demand.
That recovery is partial. The buyer pays the full fabrication premium and receives only the portion the market will still bear when the piece changes hands again.
The practical measure of cost is therefore the round trip: the difference between what a size is bought at and what the same size is bid at on the way out.
Size is a trade between cost and divisibility
A large bar is the cheaper way to hold a given weight, but it can only be sold whole unless it is sent back to a refiner and recast.
Smaller units cost more to acquire and give the holder the ability to sell part of a position without disturbing the rest of it.
Holders who expect to sell in stages pay for that flexibility deliberately, and holders who expect to hold in one block generally do not.