Yeah, the mind boggles, but you could be worth a billion bucks (asset wise) and still get a full subsidy from the ACA if you income is in the low 30K range.
In other words, just like rmitchell just said, the current ACA is only about income, not your 401K balance (or real estate, whatever).
I'm in the same boat, nice healthy 401K's and IRA's, but low income (retired, on modest pension). For such a situation, one does indeed have to take care not to draw money from a 401K/IRA, as that withdrawal becomes "income", and would affect the ACA subsidy. (We're living off of the small remainder of our non-401K/IRA savings (after tax money), untaill on Medicare in a couple years, at which time I'll no longer need an ACA subsidy).
Looks like 2020 will be unchanged basically, as of now, at least. It has been a real touch-and-go situation for the ACA in recent years, for obvious reasons, but it still keeps hanging in there. I suspect 2020 will be the last year of status quo. Of course I thought that back in 2018, then 2019...