Prices of commodities are global if they can be shipped. Gold has only one price. There’s no difference in a Bitcoin price if it’s mined in the US versus abroad.
Not quite, there is a world price, but shipping and storage means that your local price can be different.
In agriculture we call it bias, and elevators post this price on the sign trying to get farmers to sell. It is understood when you bring in a load of corn they pay you the Chicago price minus the bias and the Chicago price is well known (rural radio stations report it every half hour), while the bias can be very different between two companies in the same small town. (In reality most corn is on a contract with prices set months before, but there is always a small percent not on contract)
Likewise, oil at the well is worth less than at the refinery, and the difference is about the shipping costs (though I suspect shipping is all contracted out and so you won't find the real difference anywhere)
I'm sure gold is the same, but I have less insight into that market.
When you actually sell/buy gold, it’s the same. Rather than being one bias price (due to one commodity form - like a bushel of corn ears), it also has the element of product/form and associated spread/premium/discount (depending on the type of transaction, location, local market forces, etc).
All buy prices generally will be lower than sell prices (hence spread), no matter what. Everyone needs to get enough of a percentage to make a transaction happen, after all. It’s not a charity.
Also for instance with Gold, raw gold dust or random blobs of unattributed melt will always sell at a discount compared to an authenticated coin or bar of the same purity (maybe as much as 10% or more), due to difficulty in figuring out it’s actual purity and ability to sell it on.
If someone is operating a mine/refinery, they can negotiate something better if they have a good long term track record, of course.
A easily validated coin or bar, for instance, might even be sellable same day to a retail customer, where dust or a random no name bar might require tracking down a wholesale buyer (and get a lower price) and require more time and work to validate - and have more risk for the middleman due to fraud or price slippage.
Some coins or bars will also not be in high demand at the moment, and require a larger spread to be worth it for a given buyer.
Certain high demand or standardized products will also be able to demand a premium (American eagles, or Canadian maple leafs, or whatever is in vogue now.). Sometimes as high as $75 or $100 above normal spot.
Standardized (and tracked/serialized) COMEX bars are used to set the market price, but are huge, and not something that folks can typically get value from by holding in their hand, as they need to always have a documented chain of custody or go through an expensive recertification.
So smaller amounts will also have a corresponding larger spread.
Same for all commodities. They are standardized, but that sets the baseline. Almost every actual individual product has some normal offset from it for whatever specific difference applies. That difference includes things like quality, transport/delivery costs from its current location, usability/marketability of that specific form, etc.
For example, nat gas prices in the US are usually cheaper than the price in Europe. For the last year, due to recent events, the price differential has been a lot bigger too.
on top of that, there are contracts. So Japan might pay a different price to Europe, but that might be because they bought a contract 12 months ago for today's price
That differential is mostly due to shipping and limited supply though. Creating and processing LNG is expensive, and there's limited worldwide infrastructure to make it.
Natural gas is not very portable in gas form. LNG so it can be shipped is kind of expensive on both sides, so having pipeline access is really important.
