thatには、主格、目的格の２つしかなく、格による形の変化はない。
'That' has only the two cases, nominative and objective, and it does not inflect depending on the case.

いろいろ考えてみると私の主観ですが、プレゼントはどれだけ気持ちがこめられているかで価値がかわってくるのだと思います。
All things considered, and it's just my opinion but, I think that the value of a present changes depending on how much thought is put into it.