I've got a 2011 BMW X5 diesel with 189k miles on it. The DPF went out at around 150k, which is roughly the expected lifetime from my understanding. The part alone is ~$4000. Regardless of living in CA, I'd have replaced it anyway because I think it's the right thing to do. (I didn't want a non-DPF diesel that was emitting lots of PM2.5s when I made my purchase).

That said, many people would prefer the money in their bank account. And if I had decided to sell it rather than fix, no doubt it would have gone to someone looking to delete the DPF.