を買わせた

made someone buy

→ を
phrase Rare #30,879
made someone buy The past causative form of 買う, used to say that someone made, persuaded, or tricked another person into buying something. を marks the person who was made to buy.
JA: 兄は私を説得して新しいパソコンを買わせた。
EN: My brother persuaded me to buy a new computer.

私の妻はを説得して新車を買わせた

My wife persuaded me to buy a new car.

私は彼を説得して新しいベッドを買わせた

I persuaded him to buy a new bed.

私はついに彼を説得してそれを買わせた

I finally convinced him to buy it.

とうとうそのセールスマンを説得して高価な機械を買わせた

In the end, the salesman persuaded me to buy an expensive machine.

セールスマン両親を説得して百科事典を買わせた

The salesman persuaded my parents to buy an encyclopedia.