"Don't major in art history at a $30k/year school unless we win the lottery"
If you put it in precisely those terms, I would wager one of your kids will, of all possible career choices, choose to major in art history for exactly $30k/year.
Any parent will tell you that inducing a desired teenager behavior while maintaining the illusion of free will is a simple wording trick:
"I would love to see you succeed in any career you choose; of course, society values things very materialistically, for example an art major will never afford a fancy car and clothes, a big house with a pool and trips around the world. But you will have your love of art and lots of art albums if that's what really maters to you."
I disagree here. Telling our kids what they should do is a good-sized chunk of a parent's job, all the way from "Don't touch that stove" to "Pick a public place to meet strangers from the internet." "Don't major in art history at a $30k/year school unless we win the lottery" is the same class of advice, and you can be sure my kids will hear it from me.