Under ACA medical plans deductibles are capped at "For 2017, your out-of-pocket maximum can be no more than $7,150 for an individual plan and $14,300 for a family plan before marketplace subsidies."[1]

[1] https://obamacarefacts.com/health-insurance/out-of-pocket-ma...

Not sure if only plans in the ACA system must meet this requirement or that private companies cannot even offer say a $50,000 deductible plan with a $3 mil cap.