You can’t buy your kids clever. What’s more, if they’re merely above average, by sending them to some hideous Holland Park hothouse, you’re probably buying them miserable. — Alex Proud, "Your child is not a genius. Get over it"
As far as I know, clever and miserable are both adjectives, not nouns. So why were they used with to buy? Is this an idiomatic way of saying You can't buy your kids intelligence and you're probably buying them (moral) misery? If so, what is the idiom used here? I'm not familiar with it.