I have an HSA and a HDHP, and it is vastly more cost effective (for me) than the plans available on the ACA website.
Goddamnit do any of you people read what I wrote? THE PLANS ON THE ACA WEBSITE ARE NOT COMPARABLE TO HSA PLANS.
Of course they cost more than your HSA-eligible plan; they have more coverage and lower deductibles!
Back before the ACA, when I was shopping for health insurance on sites like ehealthinsurance.com, there were in fact plans that had the same coverage and the same deductible as an HSA plan offered by the same company. In fact, the plans were exactly the same except that one version was HSA-eligible, and the other was not. The only difference was the fact that the HSA-eligible version of the otherwise exact same, completely comparable plan had much higher premiums than the non-HSA-eligible version.
The ACA has only made things related to HSA-eligible plans worse because a) they're a lot less common now in general (for example, my employer no longer offers one, but apparently used to), and b) you can't buy one from the federal exchange / ACA website.
FYI, I would love to have an HSA-eligible plan since my wife and I are both under 30 years old and healthy, yet just the employee-paid half of my wife's coverage costs something like $400/month. But I can't have an HSA-eligible plan, because neither my employer nor the ACA website offer one, and I'm not about to buy an individual plan outside the ACA website because that fails to qualify for the subsidy and would therefore be even more exorbitantly expensive. (It also doesn't help that by the time the people running the ACA website got their shit together the open enrollment period at my job had already ended and now I'm locked in for the year...)