買ってやる

buy for someone

→ 買う
phrase Uncommon #10,594
buy for someone A form of 買ってあげる meaning to buy something for someone as a favor. It can sound casual, masculine, or condescending depending on the context; 買ってあげる is generally more neutral and polite.
JA: 今日は私が君に夕飯を買ってやるよ。
EN: I'll buy you dinner today.

買ってやる

I'll buy it for you.

— フォーリング・ダウン (1993)

私は娘にカメラを買ってやるつもりです

I’m planning to buy my daughter a camera.

なら買ってやる

If it’s clothes, I’ll buy them for you.

— マルコムX (1992)

そろそろ娘に適当なパソコンを買ってやる時期だ私は考えている

I think it’s about time I bought my daughter a suitable computer.

私は彼女に新しいドレス買ってやる余裕がない

I can't afford to buy her a new dress.

これで携帯電話買ってやる

I'll buy you a cell phone with this.

— グエムル -漢江の怪物- (2006)

買ってやる

I'll buy it for you.

— 自転車泥棒 (1948)

私は息子に腕時計買ってやるつもりです

I’m planning to buy my son a wristwatch.