[Grammar] ...than I could afford them

[kadioguy]

She bought more shoes than I could afford them. ('them' means 'shoes')
She bought more shoes than they were needed. ('they' means 'shoes')
He worries more than it is necessary. ('it' means 'worry')

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Are these sentence above grammatically correct, but sound unnatural?
(Use 'than' as an conjunction)

 

[GoesStation]

She bought more shoes than I could afford [STRIKE]them[/STRIKE]. ('them' means 'shoes')
She bought more shoes than [STRIKE]they[/STRIKE] were needed. ('they' means 'shoes')
He worries more than [STRIKE]it is[/STRIKE] necessary. ('it' means 'worry')

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Are these sentence above grammatically correct, but sound unnatural?
(Use 'than' as an conjunction)

You used than correctly in all three sentences, but they all contained extra pronouns which made them wrong. I've struck out the excess pronouns (and one verb) above. They're all natural with my corrections.

 

[GoesStation]

I should have noted that He worries more than is necessary is also grammatically correct. Only the pronoun "it" was wrong in your version of that sentence.