"item" or "items"?

Teleostomi

The concept of using money or some other item of value to buy things is as old as human existence itself.

Is this "item" just a typographical error? Or should it be "items" instead?

I would go with the singular, although I think the plural is o.k. as well.

Why singular? There are a lot of things with which to barter. I think it is rather strange to limit it to just one.

Money itself is one item. There may be many alternatives, but the idea is that you use only one at a time. Some other item means another, undefined item.

Teleostomi

The concept of using money or some other item of value to buy things is as old as human existence itself.

Is this "item" just a typographical error? Or should it be "items" instead?

Money is uncountable. I think the author used item in an analogous way here, in the sing

No, I'd say item is always countable. If you want to use the plural, you must say "other items" without "some". Some here is not a partitive, which would mean "a certain quantity/number". It's the same as in something, which is singular.
What about Do you have a cat, or some other pet?

Thanks!

J Louis, you're explanation convinced me.

"some other item" is similar to "something else" that is singular.