Is it grammatically correct to seperate a complete sentence and an incomplete sentence with a semi-colon? [closed]

A common pattern in English is to separate two complete sentences with a semi-colon.

For example,

John was hurt; he knew she only said it to upset him.

"John was hurt" is a complete sentence, and so is, "he knew she only said it to upset him."

The pattern is:

[sentence] [semi-colon] [sentence]

As you know, we usually use a semi-colon, instead of a period, when it is important to take the two sentences together to form the whole idea.

However, in what cases (if any) is the following pattern valid?

[complete sentence] [semi-colon] [incomplete sentence]

Examples:

They’re not very expensive; maybe $10.
Both are unconscious; no clear prognosis.

The venerable Warriner's English Grammar and Composition regards the examples in which an incomplete clause follows the semicolon as incorrect. According to Warriner, a semicolon may join two independent clauses, both of which should be possessed of a subject and verb.