I'm actually quite curious about this.
Especially in a modern society, that decision-making process is no more relevant than asking whether it's OK to dump toxic waste into the river, because the fines could be cheaper than processing such waste safely.
If insurance companies can't make money (or at least break even) for a certain population then they are't a viable means of making sure care is payed for, and we need to develop alternate policies to make things work.
So it's actually very very relevant to understand the decision-making process of insurance companies in these situations.
If Obamacare-as-a-block is business they don't want, they shouldn't have to take it. If it's a subset of individuals, I'm less sympathetic.
And if the Obamacare exchanges don't work, that's no good either!
As I said elsewhere, the economics of health care are very challenging.
That's why I find these questions irrelevant.
This type of thing isn't so much a pre-existing condition as much as they are "I had a health issue that was more severe than a simple infection". It isn't the same as "I have diabetes" or "I have chronic issues with x", which can cause expenses.