Sentence Fragments
There are many instances of working conditions in the craft industry that are not economically sustainable. For example, having a monthly income lower than the national minimum wage average.
This may appear harmless, but it is grammatically incorrect. It is generally referred to as a sentence fragment. The sentence is incomplete because it does not have a subject and a verb.
🇮🇩
Indonesian IELTS candidates often introduce examples in this way. Perhaps that's how it's done in Bahasa Indonesia?
The safest way to introduce an example, and to maintain correct grammar, is following a comma:
There are many instances of working conditions in the craft industry that are not economically sustainable, for example having a monthly income lower than the national minimum wage average.
Alternatively you can follow For example with an independent clause:
There are many instances of working conditions in the craft industry that are not economically sustainable. For example, having a monthly income lower than the national minimum wage average is not sustainable.
For more information about clauses, check out the video conjunction sandwich.