No, you cannot make an ornate painted metal wall bracket for "cheap", ie for considerably less than $4, using any process that I would call "DIY" in the context of hanging a plant. If the question was "I have a metal shop, what's the cheapest approach to reproducing this piece", perhaps there would be a much-less-than-$4 one but that's not the question and this wouldn't be the forum.
A plant can be hung with a screw hook in a ceiling joist and a piece of string. Total cost 50 cents.

If you need to hang it from a wall you can get offcut scraps of wood from a hardware store for free (or pick up a discarded flood-damaged piece of furniture off the street and use that for wood) and make wood L brackets. You'll still need about 50 cents for screws.
