In addition to guaranteed issue, the Obamacare plans have (1) an annual out-of-pocket limit (2) no annual or lifetime limit on benefits (3) an absolute right to renewal.
These features raise the cost substantially compared to previous plans on the individual market. The classic example is if you get cancer and need $2 million in treatment. If your plan had 20% coinsurance, or a $1 million lifetime limit, then you'd be in rough shape. And if the insurance company dropped you when you got sick, on the grounds that you forgot to disclose some trivial and unrelated illness on your application, then you'd be in really rough shape.
The things that make Obamacare expensive are the features that don't show up on the sticker -- because they are now required of all plans. Guaranteed issue is the major one, because they prevent sick people from being washed out of the actuarial pool. All of these features are things that you hope you will never need to "take advantage" of. If you waste your money buying them, that's actually not a bad outcome.
http://en.wikipedia.org/wiki/Pre-existing_condition#Current_...
I've talked to dozens of people since then and come to the conclusion that "functioning human female reproductive system" is, in essence, a coverage-denying preexisting condition in many US states.
Another thing that happens --- particularly in California, lest you think this is an IL problem --- is that comparatively minor medical conditions were used as proxies for rare but expensive conditions. For instance, if you were a woman with abnormal cramping, you might be default-denied based on a simple blacklist of uninsurable conditions because insurers were scared that might presage something expensive down the road.
The preexisting condition and recission policies of insurers prior to Obamacare were a national disgrace.