The Shield +1 is the same price as a base shield.

The Shield +1 inventory border (the square outline) is not highlighted, even though it is a magic item.

The Iron Banded Shield has a bright border like a magic item, but isn't one.

I think the banded shield used to give advantage on perception checks.

I'm not sure if it still does that or not.

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In regards to odd pricing, the Steelforged Sword is a +1 short sword, but it has a low monetary value attached to it.