How opaque should a secondary text be?

There is a debate between the UI and the UX staff about "How opaque should a secondary text be?"

This is the example UI:

enter image description here

The design is meant to be minimalist. We use only black & white, no colors at all. And there is a small text: "Only > $10 orders".

The UX staff wants to make it 80% opaque (see last item) because it is important for the end-user to be aware of it. The UI staff wants to make it 15% opaque (see first item) otherwise they feel the minimalist design gets broken.

From a UI/UX objective point of view. How opaque should secondary texts be?

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