As someone who's a bit older (27) with a family (wife and kid), I'd agree that eventually money becomes an issue. Even if I get some great offers, I still have to weigh the cost of putting off financial goals for another 5 plus years. And spending several more years attempting to find a TT position after that isn't feasible. Fortunately for me, I'm coming from a career field where a PhD is both beneficial and extremely valuable money wise. If I didn't have that to fall back on, I wouldn't even be considering this.