Albert Barnes on Mark 12:43

This poor widow hath cast more in, etc. That is, more in proportion to her means, and therefore more that was acceptable to God. He does not mean that this was more in value than all which the others had put in, but it showed more love to the sacred cause, more self-denial, and of course more sincerity in what she did. This is the rule by which God will reward us. Compare 2Cor 8:12.

(x) "this poor widow" 2Cor 8:2,12